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GD50 - Pong

Posted on Edited on In Disqus: 62k 56 mins.

两年前,在炎热夏日的宿舍房间里初学写C.
那时看到了这个游戏制作公开课,因为C都写得极其头大,打开三分钟决定搁置.
上个月一看:卧槽这公开课今年截止.
于是试图在死线前摸点笔记.

第一个project是经典小游戏Pong,附录Github代码.




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这个课程使用的是lua语言,run游戏的是love 2D.

Download&Getting Started

摸了一下还是直接drag的方式最方便run.

Otherwise, the easiest way to run the game is to drag the folder onto either love.exe or a shortcut to love.exe. Remember to drag the folder containing main.lua, and not main.lua itself.

function

love.load()

  • Used for initializing our game state at the very beginning of program execution. Load function肯定自带有,这是overwrite初始function. Love2D默认read main.lua file.

love.update(dt) - dt:delta time

  • Called each frame by LÖVE; dt will be the elapsed time in seconds since the last frame, and we can use this to scale any changes in our game for even behavior across frame rates.

love.draw()

  • Called each frame by LÖVE after update for drawing things to the screen once they’ve changed.

LÖVE2D expects these functions to be implemented in main.lua and calls them internally; if we don’t define them, it will still function, but our game will be fundamentally incomplete, at least if update or draw are missing!

love.graphics.printf(text, x, y, [width], [align])

  • Versatile print function that can align text left, right, or center on the screen.

love.window.setMode(width, height, params)

  • Used to initialize the window’s dimensions and to set parameters like vsync (vertical sync), whether we’re fullscreen or not, and whether the window is resizable after startup. Won’t be using past this example in favor of the push virtual resolution library, which has its own method like this, but useful to know if encountered in other code.

source code

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--[[
    GD50 2018
    Pong Remake

    pong-0
    "The Day-0 Update"

    -- Main Program --
]]

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    love.window.setMode(WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen, updated or otherwise.
]]
function love.draw()
    love.graphics.printf(
        'Hello Pong!',          -- text to render
        0,                      -- starting X (0 since we're going to center it based on width)
        WINDOW_HEIGHT / 2 - 6,  -- starting Y (halfway down the screen)
        WINDOW_WIDTH,           -- number of pixels to center within (the entire screen here)
        'center')               -- alignment mode, can be 'center', 'left', or 'right'
end




1

下一步更改了resolution.

function

love.graphics.setDefaultFilter(min, mag)

  • Sets the texture scaling filter when minimizing and magnifying textures and fonts; default is bilinear, which causes blurriness, and for our use cases we will typically want nearest-neighbor filtering (‘nearest’), which results in perfect pixel upscaling and downscaling, simulating a retro feel.
    当love2D run text or image的时候,会apply一个default filter.

love.keypressed(key)

  • A LÖVE2D callback function that executes whenever we press a key, assuming we’ve implemented this in our main.lua, in the same vein as love.load(), love.update(dt), and love.draw().

love.event.quit()

  • Simple function that terminates the application.

source code

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--[[
    GD50 2018
    Pong Remake

    pong-1
    "The Low-Res Update"

    -- Main Program --
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
-- 导入library

push = require 'push'

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

-- 这一步是原本432*243大小的图像之后render成 1280*720,看起来像老游戏

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    -- use nearest-neighbor filtering on upscaling and downscaling to prevent blurring of text
    -- and graphics; try removing this function to see the difference!
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- initialize our virtual resolution, which will be rendered within our
    -- actual window no matter its dimensions; replaces our love.window.setMode call
    -- from the last example
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)
    -- keys can be accessed by string name
    if key == 'escape' then
        -- function LÖVE gives us to terminate application
        love.event.quit()
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()
    -- begin rendering at virtual resolution
    push:apply('start')

    -- condensed onto one line from last example
    -- note we are now using virtual width and height now for text placement
    love.graphics.printf('Hello Pong!', 0, VIRTUAL_HEIGHT / 2 - 6, VIRTUAL_WIDTH, 'center')

    -- end rendering at virtual resolution
    push:apply('end')
end

这个folder下有两个file.
上文是main.lua ,下文是push.lua .

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-- push.lua v0.4

-- Copyright (c) 2020 Ulysse Ramage
-- Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
-- The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

local love11 = love.getVersion() == 11
local getDPI = love11 and love.window.getDPIScale or love.window.getPixelScale
local windowUpdateMode = love11 and love.window.updateMode or function(width, height, settings)
  local _, _, flags = love.window.getMode()
  for k, v in pairs(settings) do flags[k] = v end
  love.window.setMode(width, height, flags)
end

local push = {

  defaults = {
    fullscreen = false,
    resizable = false,
    pixelperfect = false,
    highdpi = true,
    canvas = true,
    stencil = true
  }

}
setmetatable(push, push)

function push:applySettings(settings)
  for k, v in pairs(settings) do
    self["_" .. k] = v
  end
end

function push:resetSettings() return self:applySettings(self.defaults) end

function push:setupScreen(WWIDTH, WHEIGHT, RWIDTH, RHEIGHT, settings)

  settings = settings or {}

  self._WWIDTH, self._WHEIGHT = WWIDTH, WHEIGHT
  self._RWIDTH, self._RHEIGHT = RWIDTH, RHEIGHT

  self:applySettings(self.defaults) --set defaults first
  self:applySettings(settings) --then fill with custom settings

  windowUpdateMode(self._RWIDTH, self._RHEIGHT, {
    fullscreen = self._fullscreen,
    resizable = self._resizable,
    highdpi = self._highdpi
  })

  self:initValues()

  if self._canvas then
    self:setupCanvas({ "default" }) --setup canvas
  end

  self._borderColor = {0, 0, 0}

  self._drawFunctions = {
    ["start"] = self.start,
    ["end"] = self.finish
  }

  return self
end

function push:setupCanvas(canvases)
  table.insert(canvases, { name = "_render", private = true }) --final render

  self._canvas = true
  self.canvases = {}

  for i = 1, #canvases do
    push:addCanvas(canvases[i])
  end

  return self
end
function push:addCanvas(params)
  table.insert(self.canvases, {
    name = params.name,
    private = params.private,
    shader = params.shader,
    canvas = love.graphics.newCanvas(self._WWIDTH, self._WHEIGHT),
    stencil = params.stencil or self._stencil
  })
end

function push:setCanvas(name)
  if not self._canvas then return true end
  local canvasTable = self:getCanvasTable(name)
  return love.graphics.setCanvas({ canvasTable.canvas, stencil = canvasTable.stencil })
end
function push:getCanvasTable(name)
  for i = 1, #self.canvases do
    if self.canvases[i].name == name then
      return self.canvases[i]
    end
  end
end
function push:setShader(name, shader)
  if not shader then
    self:getCanvasTable("_render").shader = name
  else
    self:getCanvasTable(name).shader = shader
  end
end

function push:initValues()
  self._PSCALE = (not love11 and self._highdpi) and getDPI() or 1

  self._SCALE = {
    x = self._RWIDTH/self._WWIDTH * self._PSCALE,
    y = self._RHEIGHT/self._WHEIGHT * self._PSCALE
  }

  if self._stretched then --if stretched, no need to apply offset
    self._OFFSET = {x = 0, y = 0}
  else
    local scale = math.min(self._SCALE.x, self._SCALE.y)
    if self._pixelperfect then scale = math.floor(scale) end

    self._OFFSET = {x = (self._SCALE.x - scale) * (self._WWIDTH/2), y = (self._SCALE.y - scale) * (self._WHEIGHT/2)}
    self._SCALE.x, self._SCALE.y = scale, scale --apply same scale to X and Y
  end

  self._GWIDTH = self._RWIDTH * self._PSCALE - self._OFFSET.x * 2
  self._GHEIGHT = self._RHEIGHT * self._PSCALE - self._OFFSET.y * 2
end

function push:apply(operation, shader)
  self._drawFunctions[operation](self, shader)
end

function push:start()
  if self._canvas then
    love.graphics.push()
    love.graphics.setCanvas({ self.canvases[1].canvas, stencil = self.canvases[1].stencil })

  else
    love.graphics.translate(self._OFFSET.x, self._OFFSET.y)
    love.graphics.setScissor(self._OFFSET.x, self._OFFSET.y, self._WWIDTH*self._SCALE.x, self._WHEIGHT*self._SCALE.y)
    love.graphics.push()
    love.graphics.scale(self._SCALE.x, self._SCALE.y)
  end
end

function push:applyShaders(canvas, shaders)
  local _shader = love.graphics.getShader()
  if #shaders <= 1 then
    love.graphics.setShader(shaders[1])
    love.graphics.draw(canvas)
  else
    local _canvas = love.graphics.getCanvas()

    local _tmp = self:getCanvasTable("_tmp")
    if not _tmp then --create temp canvas only if needed
      self:addCanvas({ name = "_tmp", private = true, shader = nil })
      _tmp = self:getCanvasTable("_tmp")
    end

    love.graphics.push()
    love.graphics.origin()
    local outputCanvas
    for i = 1, #shaders do
      local inputCanvas = i % 2 == 1 and canvas or _tmp.canvas
      outputCanvas = i % 2 == 0 and canvas or _tmp.canvas
      love.graphics.setCanvas(outputCanvas)
      love.graphics.clear()
      love.graphics.setShader(shaders[i])
      love.graphics.draw(inputCanvas)
      love.graphics.setCanvas(inputCanvas)
    end
    love.graphics.pop()

    love.graphics.setCanvas(_canvas)
    love.graphics.draw(outputCanvas)
  end
  love.graphics.setShader(_shader)
end

function push:finish(shader)
  love.graphics.setBackgroundColor(unpack(self._borderColor))
  if self._canvas then
    local _render = self:getCanvasTable("_render")

    love.graphics.pop()

    local white = love11 and 1 or 255
    love.graphics.setColor(white, white, white)

    --draw canvas
    love.graphics.setCanvas(_render.canvas)
    for i = 1, #self.canvases do --do not draw _render yet
      local _table = self.canvases[i]
      if not _table.private then
        local _canvas = _table.canvas
        local _shader = _table.shader
        self:applyShaders(_canvas, type(_shader) == "table" and _shader or { _shader })
      end
    end
    love.graphics.setCanvas()

    --draw render
    love.graphics.translate(self._OFFSET.x, self._OFFSET.y)
    local shader = shader or _render.shader
    love.graphics.push()
    love.graphics.scale(self._SCALE.x, self._SCALE.y)
    self:applyShaders(_render.canvas, type(shader) == "table" and shader or { shader })
    love.graphics.pop()

    --clear canvas
    for i = 1, #self.canvases do
      love.graphics.setCanvas(self.canvases[i].canvas)
      love.graphics.clear()
    end

    love.graphics.setCanvas()
    love.graphics.setShader()
  else
    love.graphics.pop()
    love.graphics.setScissor()
  end
end

function push:setBorderColor(color, g, b)
  self._borderColor = g and {color, g, b} or color
end

function push:toGame(x, y)
  x, y = x - self._OFFSET.x, y - self._OFFSET.y
  local normalX, normalY = x / self._GWIDTH, y / self._GHEIGHT

  x = (x >= 0 and x <= self._WWIDTH * self._SCALE.x) and normalX * self._WWIDTH or nil
  y = (y >= 0 and y <= self._WHEIGHT * self._SCALE.y) and normalY * self._WHEIGHT or nil

  return x, y
end

--doesn't work - TODO
function push:toReal(x, y)
  return x + self._OFFSET.x, y + self._OFFSET.y
end

function push:switchFullscreen(winw, winh)
  self._fullscreen = not self._fullscreen
  local windowWidth, windowHeight = love.window.getDesktopDimensions()

  if self._fullscreen then --save windowed dimensions for later
    self._WINWIDTH, self._WINHEIGHT = self._RWIDTH, self._RHEIGHT
  elseif not self._WINWIDTH or not self._WINHEIGHT then
    self._WINWIDTH, self._WINHEIGHT = windowWidth * .5, windowHeight * .5
  end

  self._RWIDTH = self._fullscreen and windowWidth or winw or self._WINWIDTH
  self._RHEIGHT = self._fullscreen and windowHeight or winh or self._WINHEIGHT

  self:initValues()

  love.window.setFullscreen(self._fullscreen, "desktop")
  if not self._fullscreen and (winw or winh) then
    windowUpdateMode(self._RWIDTH, self._RHEIGHT) --set window dimensions
  end
end

function push:resize(w, h)
  if self._highdpi then w, h = w / self._PSCALE, h / self._PSCALE end
  self._RWIDTH = w
  self._RHEIGHT = h
  self:initValues()
end

function push:getWidth() return self._WWIDTH end
function push:getHeight() return self._WHEIGHT end
function push:getDimensions() return self._WWIDTH, self._WHEIGHT end

return push




2

画出paddle和球.

function

love.graphics.newFont(path, size)

  • Loads a font file into memory at a specific path, setting it to a specific size, and storing it in an object we can use to globally change the currently active font that LÖVE2D is using to render text (functioning like a state machine). Deafult is Arial.

love.graphics.setFont(font)

  • Sets LÖVE2D’s currently active font (of which there can only be one at a time) to a passed-in font object that we can create using love.graphics.newFont.

love.graphics.clear(r, g, b, a)

  • Wipes the entire screen with a color defined by an RGBA set, each component of which being from 0-255.

love.graphics.rectangle(mode, x, y, width, height)

  • Draws a rectangle onto the screen using whichever our active color is (love.graphics.setColor, which we don’t need to use in this particular project since most everything is white, the default LÖVE2D color). mode can be set to ‘fill’ or ‘line’, which result in a filled or outlined rectangle, respectively, and the other four parameters are its position and size dimensions. This is the cornerstone drawing function of the entirety of our Pong implementation!

source code

这次文件夹下有main.lua, push.lua and font.ttf .

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--[[
    GD50 2018
    Pong Remake

    pong-2
    "The Rectangle Update"
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
push = require 'push'

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- more "retro-looking" font object we can use for any text
    smallFont = love.graphics.newFont('font.ttf', 8)

    -- set LÖVE2D's active font to the smallFont obect
    love.graphics.setFont(smallFont)

    -- initialize window with virtual resolution
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)
    -- keys can be accessed by string name
    if key == 'escape' then
        -- function LÖVE gives us to terminate application
        love.event.quit()
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()
    -- begin rendering at virtual resolution
    push:apply('start')

    -- clear the screen with a specific color; in this case, a color similar
    -- to some versions of the original Pong
    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    -- draw welcome text toward the top of the screen
    love.graphics.printf('Hello Pong!', 0, 20, VIRTUAL_WIDTH, 'center')

    --
    -- paddles are simply rectangles we draw on the screen at certain points,
    -- as is the ball
    --

    -- render first paddle (left side)
    love.graphics.rectangle('fill', 10, 30, 5, 20)

    -- render second paddle (right side)
    love.graphics.rectangle('fill', VIRTUAL_WIDTH - 10, VIRTUAL_HEIGHT - 50, 5, 20)

    -- render ball (center) 减2是因为ball本身有2 pixel
    love.graphics.rectangle('fill', VIRTUAL_WIDTH / 2 - 2, VIRTUAL_HEIGHT / 2 - 2, 4, 4)

    -- end rendering at virtual resolution
    push:apply('end')
end




3

让paddle动起来!

function

love.keyboard.isDown(key)

  • Returns true or false depending on whether the specified key is currently held down; differs from love.keypressed(key) in that this can be called arbitrarily and will continuously return true if the key is pressed down, where love.keypressed(key) will only fire its code once every time the key is initially pressed down. However, since we want to be able to move our paddles up and down by holding down the appropriate keys, we need a function to test for longer periods of input, hence the use of love.keyboard.isDown(key)!
    This returns true or false.

source code

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--[[
    GD50 2018
    Pong Remake

    pong-3
    "The Paddle Update"
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
push = require 'push'

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

-- paddle移动速度; multiplied by dt in update
PADDLE_SPEED = 200

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- more "retro-looking" font object we can use for any text
    smallFont = love.graphics.newFont('font.ttf', 8)

    -- larger font for drawing the score on the screen
    scoreFont = love.graphics.newFont('font.ttf', 32)

    -- set LÖVE2D's active font to the smallFont obect
    love.graphics.setFont(smallFont)

    -- initialize window with virtual resolution
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })

    -- initialize score variables, used for rendering on the screen and keeping
    -- track of the winner
    player1Score = 0
    player2Score = 0

    -- paddle positions on the Y axis (they can only move up or down)
    player1Y = 30
    player2Y = VIRTUAL_HEIGHT - 50
end

--[[
    Runs every frame, with "dt" passed in, our delta in seconds
    since the last frame, which LÖVE2D supplies us.
]]
function love.update(dt)
    -- player 1 movement
    if love.keyboard.isDown('w') then
        -- add negative paddle speed to current Y scaled by deltaTime,这里的横线是负的意思
        player1Y = player1Y + -PADDLE_SPEED * dt
    elseif love.keyboard.isDown('s') then
        -- add positive paddle speed to current Y scaled by deltaTime
        player1Y = player1Y + PADDLE_SPEED * dt
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        -- add negative paddle speed to current Y scaled by deltaTime
        player2Y = player2Y + -PADDLE_SPEED * dt
    elseif love.keyboard.isDown('down') then
        -- add positive paddle speed to current Y scaled by deltaTime
        player2Y = player2Y + PADDLE_SPEED * dt
    end
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)
    -- keys can be accessed by string name
    if key == 'escape' then
        -- function LÖVE gives us to terminate application
        love.event.quit()
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()
    -- begin rendering at virtual resolution
    push:apply('start')

    -- clear the screen with a specific color; in this case, a color similar
    -- to some versions of the original Pong
    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    -- draw welcome text toward the top of the screen
    love.graphics.setFont(smallFont)
    love.graphics.printf('Hello Pong!', 0, 20, VIRTUAL_WIDTH, 'center')

    -- draw score on the left and right center of the screen
    -- need to switch font to draw before actually printing
    love.graphics.setFont(scoreFont)
    love.graphics.print(tostring(player1Score), VIRTUAL_WIDTH / 2 - 50,
        VIRTUAL_HEIGHT / 3)
    love.graphics.print(tostring(player2Score), VIRTUAL_WIDTH / 2 + 30,
        VIRTUAL_HEIGHT / 3)

    -- render first paddle (left side), now using the players' Y variable
    love.graphics.rectangle('fill', 10, player1Y, 5, 20)

    -- render second paddle (right side)
    love.graphics.rectangle('fill', VIRTUAL_WIDTH - 10, player2Y, 5, 20)

    -- render ball (center)
    love.graphics.rectangle('fill', VIRTUAL_WIDTH / 2 - 2, VIRTUAL_HEIGHT / 2 - 2, 4, 4)

    -- end rendering at virtual resolution
    push:apply('end')
end



4

让球动起来!

function

math.randomseed(num)

  • ”Seeds” the random number generator used by Lua (math.random) with some value such that its randomness is dependent on that supplied value, allowing us to pass in different numbers each playthrough to guarantee non-consistency across different program executions (or uniformity if we want consistent behavior for testing).

os.time()

  • Lua function that returns, in seconds, the time since 00:00:00 UTC, January 1, 1970, also known as Unix epoch time
    (https://en.wikipedia.org/wiki/Unix_time).
    因为每次的时间不一样,所以可以拿来当作seed.

math.random(min, max)

  • Returns a random number, dependent on the seeded random number generator, between min and max,
    inclusive.

math.min(num1, num2)

  • Returns the lesser of the two numbers passed in.

math.max(num1, num2)

  • Returns the greater of the two numbers passed in.

source code

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--[[
    GD50 2018
    Pong Remake

    pong-4
    "The Ball Update"

    -- Main Program --
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
push = require 'push'

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

-- speed at which we will move our paddle; multiplied by dt in update
PADDLE_SPEED = 200

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- "seed" the RNG so that calls to random are always random
    -- use the current time, since that will vary on startup every time
    math.randomseed(os.time())

    -- more "retro-looking" font object we can use for any text
    smallFont = love.graphics.newFont('font.ttf', 8)

    -- set LÖVE2D's active font to the smallFont obect
    love.graphics.setFont(smallFont)

    -- initialize window with virtual resolution
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })

    -- paddle positions on the Y axis (they can only move up or down)
    player1Y = 30
    player2Y = VIRTUAL_HEIGHT - 50

    -- velocity and position variables for our ball when play starts
    ballX = VIRTUAL_WIDTH / 2 - 2
    ballY = VIRTUAL_HEIGHT / 2 - 2

    -- math.random returns a random value between the left and right number
    -- dx and dy are delta x and delta y, which represent velocity
    ballDX = math.random(2) == 1 and 100 or -100
    ballDY = math.random(-50, 50)
    -- by adding them one frame by one frame in update, ball will move

    -- game state variable used to transition between different parts of the game
    -- (used for beginning, menus, main game, high score list, etc.)
    -- we will use this to determine behavior during render and update
    gameState = 'start'
end

--[[
    Runs every frame, with "dt" passed in, our delta in seconds
    since the last frame, which LÖVE2D supplies us.
]]
function love.update(dt)
    -- player 1 movement
    if love.keyboard.isDown('w') then
        -- add negative paddle speed to current Y scaled by deltaTime
        -- now, we clamp our position between the bounds of the screen
        -- math.max returns the greater of two values; 0 and player Y
        -- will ensure we don't go above it
        player1Y = math.max(0, player1Y + -PADDLE_SPEED * dt)

        -- 用max来锁住活动范围

    elseif love.keyboard.isDown('s') then
        -- add positive paddle speed to current Y scaled by deltaTime
        -- math.min returns the lesser of two values; bottom of the egde minus paddle height
        -- and player Y will ensure we don't go below it
        player1Y = math.min(VIRTUAL_HEIGHT - 20, player1Y + PADDLE_SPEED * dt)
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        -- add negative paddle speed to current Y scaled by deltaTime
        player2Y = math.max(0, player2Y + -PADDLE_SPEED * dt)
    elseif love.keyboard.isDown('down') then
        -- add positive paddle speed to current Y scaled by deltaTime
        player2Y = math.min(VIRTUAL_HEIGHT - 20, player2Y + PADDLE_SPEED * dt)
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ballX = ballX + ballDX * dt
        ballY = ballY + ballDY * dt
    end
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)
    -- keys can be accessed by string name
    if key == 'escape' then
        -- function LÖVE gives us to terminate application
        love.event.quit()
    -- if we press enter during the start state of the game, we'll go into play mode
    -- during play mode, the ball will move in a random direction
    elseif key == 'enter' or key == 'return' then
        if gameState == 'start' then
            gameState = 'play'
        else
            gameState = 'start'

            -- start ball's position in the middle of the screen
            ballX = VIRTUAL_WIDTH / 2 - 2
            ballY = VIRTUAL_HEIGHT / 2 - 2

            -- given ball's x and y velocity a random starting value
            -- the and/or pattern here is Lua's way of accomplishing a ternary operation
            -- in other programming languages like C
            ballDX = math.random(2) == 1 and 100 or -100
            -- 这跟在C里写 math.random(2) == 1 ? 100 : -100相同
            ballDY = math.random(-50, 50) * 1.5
        end
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()
    -- begin rendering at virtual resolution
    push:apply('start')

    -- clear the screen with a specific color; in this case, a color similar
    -- to some versions of the original Pong
    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    -- draw different things based on the state of the game
    love.graphics.setFont(smallFont)

    if gameState == 'start' then
        love.graphics.printf('Hello Start State!', 0, 20, VIRTUAL_WIDTH, 'center')
    else
        love.graphics.printf('Hello Play State!', 0, 20, VIRTUAL_WIDTH, 'center')
    end

    -- render first paddle (left side), now using the players' Y variable
    love.graphics.rectangle('fill', 10, player1Y, 5, 20)

    -- render second paddle (right side)
    love.graphics.rectangle('fill', VIRTUAL_WIDTH - 10, player2Y, 5, 20)

    -- render ball (center)
    love.graphics.rectangle('fill', ballX, ballY, 4, 4)

    -- end rendering at virtual resolution
    push:apply('end')
end




4

Class update,把paddle和球换成class.
(Yeah this makes more sense.)

function

What is a class?

  • Blueprints for creating bundles of data and code that are related.
  • A “Car” class can have attributes that describe its brand, model, color, miles, and anything else descriptive; these are also known as “fields”.
  • A “Car” class can also have “methods” that define its behavior, such as “accelerate”, “turn”, “honk”, and more, which take the form of functions.
  • Objects are instantiated from these class blueprints, and it’s these concrete objects that are the physical “cars” you see on the road, as opposed to the blueprints that may exist in the factory.
  • Our Paddles and Ball are perfect simple use cases for taking some of our code and bundling it together into classes and objects.

source code

main.lua:

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--[[
    GD50 2018
    Pong Remake

    pong-5
    "The Class Update"

    -- Main Program --
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
push = require 'push'

-- the "Class" library we're using will allow us to represent anything in
-- our game as code, rather than keeping track of many disparate variables and
-- methods
--
-- https://github.com/vrld/hump/blob/master/class.lua
Class = require 'class'

-- our Paddle class, which stores position and dimensions for each Paddle
-- and the logic for rendering them
require 'Paddle'

-- our Ball class, which isn't much different than a Paddle structure-wise
-- but which will mechanically function very differently
require 'Ball'

WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

-- speed at which we will move our paddle; multiplied by dt in update
PADDLE_SPEED = 200

--[[
    Runs when the game first starts up, only once; used to initialize the game.
]]
function love.load()
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- "seed" the RNG so that calls to random are always random
    -- use the current time, since that will vary on startup every time
    math.randomseed(os.time())

    -- more "retro-looking" font object we can use for any text
    smallFont = love.graphics.newFont('font.ttf', 8)

    -- set LÖVE2D's active font to the smallFont object
    love.graphics.setFont(smallFont)

    -- initialize window with virtual resolution
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = true,
        vsync = true
    })

    -- initialize our player paddles; make them global so that they can be
    -- detected by other functions and modules
    player1 = Paddle(10, 30, 5, 20)
    player2 = Paddle(VIRTUAL_WIDTH - 10, VIRTUAL_HEIGHT - 30, 5, 20)

    -- place a ball in the middle of the screen
    ball = Ball(VIRTUAL_WIDTH / 2 - 2, VIRTUAL_HEIGHT / 2 - 2, 4, 4)

    -- game state variable used to transition between different parts of the game
    -- (used for beginning, menus, main game, high score list, etc.)
    -- we will use this to determine behavior during render and update
    gameState = 'start'
end

--[[
    Runs every frame, with "dt" passed in, our delta in seconds
    since the last frame, which LÖVE2D supplies us.
]]
function love.update(dt)
    -- player 1 movement
    if love.keyboard.isDown('w') then
        player1.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('s') then
        player1.dy = PADDLE_SPEED
    else
        player1.dy = 0
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        player2.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('down') then
        player2.dy = PADDLE_SPEED
    else
        player2.dy = 0
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ball:update(dt)
    end

    player1:update(dt)
    player2:update(dt)
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)
    -- keys can be accessed by string name
    if key == 'escape' then
        -- function LÖVE gives us to terminate application
        love.event.quit()
    -- if we press enter during the start state of the game, we'll go into play mode
    -- during play mode, the ball will move in a random direction
    elseif key == 'enter' or key == 'return' then
        if gameState == 'start' then
            gameState = 'play'
        else
            gameState = 'start'

            -- ball's new reset method
            ball:reset()
        end
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()
    -- begin rendering at virtual resolution
    push:apply('start')

    -- clear the screen with a specific color; in this case, a color similar
    -- to some versions of the original Pong
    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    -- draw different things based on the state of the game
    love.graphics.setFont(smallFont)

    if gameState == 'start' then
        love.graphics.printf('Hello Start State!', 0, 20, VIRTUAL_WIDTH, 'center')
    else
        love.graphics.printf('Hello Play State!', 0, 20, VIRTUAL_WIDTH, 'center')
    end

    -- render paddles, now using their class's render method
    player1:render()
    player2:render()

    -- render ball using its class's render method
    ball:render()

    -- end rendering at virtual resolution
    push:apply('end')
end

Ball.lua:

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--[[
    GD50 2018
    Pong Remake

    -- Ball Class --

    Author: Colton Ogden
    cogden@cs50.harvard.edu

    Represents a ball which will bounce back and forth between paddles
    and walls until it passes a left or right boundary of the screen,
    scoring a point for the opponent.
]]

Ball = Class{}

function Ball:init(x, y, width, height)
    self.x = x
    self.y = y
    self.width = width
    self.height = height

    -- these variables are for keeping track of our velocity on both the
    -- X and Y axis, since the ball can move in two dimensions
    self.dy = math.random(2) == 1 and -100 or 100
    self.dx = math.random(-50, 50)
end

--[[
    Places the ball in the middle of the screen, with an initial random velocity
    on both axes.
]]
function Ball:reset()
    self.x = VIRTUAL_WIDTH / 2 - 2
    self.y = VIRTUAL_HEIGHT / 2 - 2
    self.dy = math.random(2) == 1 and -100 or 100
    self.dx = math.random(-50, 50)
end

--[[
    Simply applies velocity to position, scaled by deltaTime.
]]
function Ball:update(dt)
    self.x = self.x + self.dx * dt
    self.y = self.y + self.dy * dt
end

function Ball:render()
    love.graphics.rectangle('fill', self.x, self.y, self.width, self.height)
end

Paddle.lua:

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--[[
    GD50 2018
    Pong Remake

    -- Paddle Class --

    Author: Colton Ogden
    cogden@cs50.harvard.edu

    Represents a paddle that can move up and down. Used in the main
    program to deflect the ball back toward the opponent.
]]

Paddle = Class{}

--[[
    The `init` function on our class is called just once, when the object
    is first created. Used to set up all variables in the class and get it
    ready for use.

    Our Paddle should take an X and a Y, for positioning, as well as a width
    and height for its dimensions.

    Note that `self` is a reference to *this* object, whichever object is
    instantiated at the time this function is called. Different objects can
    have their own x, y, width, and height values, thus serving as containers
    for data. In this sense, they're very similar to structs in C.
]]
function Paddle:init(x, y, width, height)
    self.x = x
    self.y = y
    self.width = width
    self.height = height
    self.dy = 0
end

function Paddle:update(dt)
    -- math.max here ensures that we're the greater of 0 or the player's
    -- current calculated Y position when pressing up so that we don't
    -- go into the negatives; the movement calculation is simply our
    -- previously-defined paddle speed scaled by dt
    if self.dy < 0 then
        self.y = math.max(0, self.y + self.dy * dt)
    -- similar to before, this time we use math.min to ensure we don't
    -- go any farther than the bottom of the screen minus the paddle's
    -- height (or else it will go partially below, since position is
    -- based on its top left corner)
    else
        self.y = math.min(VIRTUAL_HEIGHT - self.height, self.y + self.dy * dt)
    end
end

--[[
    To be called by our main function in `love.draw`, ideally. Uses
    LÖVE2D's `rectangle` function, which takes in a draw mode as the first
    argument as well as the position and dimensions for the rectangle. To
    change the color, one must call `love.graphics.setColor`. As of the
    newest version of LÖVE2D, you can even draw rounded rectangles!
]]
function Paddle:render()
    love.graphics.rectangle('fill', self.x, self.y, self.width, self.height)
end

class.lua:

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--[[
Copyright (c) 2010-2013 Matthias Richter

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

Except as contained in this notice, the name(s) of the above copyright holders
shall not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
]]--

local function include_helper(to, from, seen)
	if from == nil then
		return to
	elseif type(from) ~= 'table' then
		return from
	elseif seen[from] then
		return seen[from]
	end

	seen[from] = to
	for k,v in pairs(from) do
		k = include_helper({}, k, seen) -- keys might also be tables
		if to[k] == nil then
			to[k] = include_helper({}, v, seen)
		end
	end
	return to
end

-- deeply copies 'other' into 'class'. keys in 'other' that are already
-- defined in 'class' are omitted
local function include(class, other)
	return include_helper(class, other, {})
end

-- returns a deep copy of 'other'
local function clone(other)
	return setmetatable(include({}, other), getmetatable(other))
end

local function new(class)
	-- mixins
	class = class or {}  -- class can be nil
	local inc = class.__includes or {}
	if getmetatable(inc) then inc = {inc} end

	for _, other in ipairs(inc) do
		if type(other) == "string" then
			other = _G[other]
		end
		include(class, other)
	end

	-- class implementation
	class.__index = class
	class.init    = class.init    or class[1] or function() end
	class.include = class.include or include
	class.clone   = class.clone   or clone

	-- constructor call
	return setmetatable(class, {__call = function(c, ...)
		local o = setmetatable({}, c)
		o:init(...)
		return o
	end})
end

-- interface for cross class-system compatibility (see https://github.com/bartbes/Class-Commons).
if class_commons ~= false and not common then
	common = {}
	function common.class(name, prototype, parent)
		return new{__includes = {prototype, parent}}
	end
	function common.instance(class, ...)
		return class(...)
	end
end


-- the module
return setmetatable({new = new, include = include, clone = clone},
	{__call = function(_,...) return new(...) end})




5

The FPS(frame per second) Update.

function

love.window.setTitle(title) - 改个标题

  • Simply sets the title of our application window, adding a slight level of polish.

love.timer.getFPS()

  • Returns the current FPS of our application, making it easy to monitor when printed.

source code

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    -- render paddles, now using their class's render method
    player1:render()
    player2:render()

    -- render ball using its class's render method
    ball:render()

    -- new function just to demonstrate how to see FPS in LÖVE2D
    displayFPS()

    -- end rendering at virtual resolution
    push:apply('end')
end

--[[
    Renders the current FPS.
]]
function displayFPS()
    -- simple FPS display across all states
    love.graphics.setFont(smallFont)
    love.graphics.setColor(0, 255/255, 0, 255/255)
    love.graphics.print('FPS: ' .. tostring(love.timer.getFPS()), 10, 10) -- 这里的点点是合并string
end




7

终于要做撞击设定了.

function

AABB Collision Detection

Relies on all colliding entities to have “alix-aligned bounding boxes”, which simply means their collision boxes contain no rotation in our world space, which allows us to use a simple math formula to test for collision:

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if rect1.x is not > rect2.x + rect2.width and
 rect1.x + rect1.width is not < rect2.x and
 rect1.y is not > rect2.y + rect2.height and
 rect1.y + rect1.height is not < rect2.y:
 collision is true
else
 collision is false

逻辑是check四次:
A方块的左边在B方块的右边,那就不会collision.同理上下左右.

source code

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function love.update(dt)
    if gameState == 'play' then
        -- detect ball collision with paddles, reversing dx if true and
        -- slightly increasing it, then altering the dy based on the position of collision
        if ball:collides(player1) then
            ball.dx = -ball.dx * 1.03 -- this 1.03 is for speed up the game
            ball.x = player1.x + 5 -- this is for not overlap paddle collision box and the ball

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end
        if ball:collides(player2) then
            ball.dx = -ball.dx * 1.03
            ball.x = player2.x - 4 -- in this case 4 is for width of the ball

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end

        -- detect upper and lower screen boundary collision and reverse if collided
        if ball.y <= 0 then
            ball.y = 0
            ball.dy = -ball.dy
        end

        -- -4 to account for the ball's size
        if ball.y >= VIRTUAL_HEIGHT - 4 then
            ball.y = VIRTUAL_HEIGHT - 4
            ball.dy = -ball.dy
        end
    end

    -- player 1 movement
    if love.keyboard.isDown('w') then
        player1.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('s') then
        player1.dy = PADDLE_SPEED
    else
        player1.dy = 0
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        player2.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('down') then
        player2.dy = PADDLE_SPEED
    else
        player2.dy = 0
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ball:update(dt)
    end

    player1:update(dt)
    player2:update(dt)
end
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function Ball:collides(paddle)
    -- first, check to see if the left edge of either is farther to the right
    -- than the right edge of the other
    if self.x > paddle.x + paddle.width or paddle.x > self.x + self.width then
        return false
    end

    -- then check to see if the bottom edge of either is higher than the top
    -- edge of the other
    if self.y > paddle.y + paddle.height or paddle.y > self.y + self.height then
        return false
    end

    -- if the above aren't true, they're overlapping
    return true
end



8

The Score Update.

source code

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function love.update(dt)
    if gameState == 'play' then
        -- detect ball collision with paddles, reversing dx if true and
        -- slightly increasing it, then altering the dy based on the position of collision
        if ball:collides(player1) then
            ball.dx = -ball.dx * 1.03
            ball.x = player1.x + 5

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end
        if ball:collides(player2) then
            ball.dx = -ball.dx * 1.03
            ball.x = player2.x - 4

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end

        -- detect upper and lower screen boundary collision and reverse if collided
        if ball.y <= 0 then
            ball.y = 0
            ball.dy = -ball.dy
        end

        -- -4 to account for the ball's size
        if ball.y >= VIRTUAL_HEIGHT - 4 then
            ball.y = VIRTUAL_HEIGHT - 4
            ball.dy = -ball.dy
        end
    end

    -- if we reach the left or right edge of the screen,
    -- go back to start and update the score
    if ball.x < 0 then
        servingPlayer = 1
        player2Score = player2Score + 1
        ball:reset()
        gameState = 'start'
    end

    if ball.x > VIRTUAL_WIDTH then
        servingPlayer = 2
        player1Score = player1Score + 1
        ball:reset()
        gameState = 'start'
    end

    -- player 1 movement
    if love.keyboard.isDown('w') then
        player1.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('s') then
        player1.dy = PADDLE_SPEED
    else
        player1.dy = 0
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        player2.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('down') then
        player2.dy = PADDLE_SPEED
    else
        player2.dy = 0
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ball:update(dt)
    end

    player1:update(dt)
    player2:update(dt)
end



9

增加一个叫做serve的stage.

游戏的设定是一开始在start stage,需要按enter才能正经进入游戏.
serve是分别给player1和player2一次试玩的机会.
在player1 的serve时,球会往player1那里跑.

这一步的目的是,把游戏分成不同的stage来考虑(make sense!).

function

source code

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function love.load()
    -- set love's default filter to "nearest-neighbor", which essentially
    -- means there will be no filtering of pixels (blurriness), which is
    -- important for a nice crisp, 2D look
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- set the title of our application window
    love.window.setTitle('Pong')

    -- "seed" the RNG so that calls to random are always random
    -- use the current time, since that will vary on startup every time
    math.randomseed(os.time())

    -- more "retro-looking" font object we can use for any text
    smallFont = love.graphics.newFont('font.ttf', 8)

    -- larger font for drawing the score on the screen
    scoreFont = love.graphics.newFont('font.ttf', 32)

    -- set LÖVE2D's active font to the smallFont obect
    love.graphics.setFont(smallFont)

    -- initialize window with virtual resolution
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = false,
        vsync = true
    })

    -- initialize score variables, used for rendering on the screen and keeping
    -- track of the winner
    player1Score = 0
    player2Score = 0

    -- either going to be 1 or 2; whomever is scored on gets to serve the
    -- following turn
    servingPlayer = 1

    -- initialize player paddles and ball
    player1 = Paddle(10, 30, 5, 20)
    player2 = Paddle(VIRTUAL_WIDTH - 10, VIRTUAL_HEIGHT - 30, 5, 20)
    ball = Ball(VIRTUAL_WIDTH / 2 - 2, VIRTUAL_HEIGHT / 2 - 2, 4, 4)

    gameState = 'start'
end

--[[
    Runs every frame, with "dt" passed in, our delta in seconds
    since the last frame, which LÖVE2D supplies us.
]]
function love.update(dt)
    if gameState == 'serve' then -- serve state
        -- before switching to play, initialize ball's velocity based
        -- on player who last scored
        ball.dy = math.random(-50, 50)
        if servingPlayer == 1 then
            ball.dx = math.random(140, 200)
        else
            ball.dx = -math.random(140, 200)
        end
    elseif gameState == 'play' then
        -- detect ball collision with paddles, reversing dx if true and
        -- slightly increasing it, then altering the dy based on the position of collision
        if ball:collides(player1) then
            ball.dx = -ball.dx * 1.03
            ball.x = player1.x + 5

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end
        if ball:collides(player2) then
            ball.dx = -ball.dx * 1.03
            ball.x = player2.x - 4

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end
        end

        -- detect upper and lower screen boundary collision and reverse if collided
        if ball.y <= 0 then
            ball.y = 0
            ball.dy = -ball.dy
        end

        -- -4 to account for the ball's size
        if ball.y >= VIRTUAL_HEIGHT - 4 then
            ball.y = VIRTUAL_HEIGHT - 4
            ball.dy = -ball.dy
        end
    end

    -- if we reach the left or right edge of the screen,
    -- go back to start and update the score
    if ball.x < 0 then
        servingPlayer = 1
        player2Score = player2Score + 1
        ball:reset()
        gameState = 'serve'
    end

    if ball.x > VIRTUAL_WIDTH then
        servingPlayer = 2
        player1Score = player1Score + 1
        ball:reset()
        gameState = 'serve'
    end

    -- player 1 movement
    if love.keyboard.isDown('w') then
        player1.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('s') then
        player1.dy = PADDLE_SPEED
    else
        player1.dy = 0
    end

    -- player 2 movement
    if love.keyboard.isDown('up') then
        player2.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('down') then
        player2.dy = PADDLE_SPEED
    else
        player2.dy = 0
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ball:update(dt)
    end

    player1:update(dt)
    player2:update(dt)
end

--[[
    Keyboard handling, called by LÖVE2D each frame;
    passes in the key we pressed so we can access.
]]
function love.keypressed(key)

    if key == 'escape' then
        love.event.quit()
    -- if we press enter during either the start or serve phase, it should
    -- transition to the next appropriate state
    elseif key == 'enter' or key == 'return' then
        if gameState == 'start' then
            gameState = 'serve'
        elseif gameState == 'serve' then
            gameState = 'play'
        end
    end
end

--[[
    Called after update by LÖVE2D, used to draw anything to the screen,
    updated or otherwise.
]]
function love.draw()

    push:apply('start')

    -- clear the screen with a specific color; in this case, a color similar
    -- to some versions of the original Pong
    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    love.graphics.setFont(smallFont)

    displayScore()

    if gameState == 'start' then
        love.graphics.setFont(smallFont)
        love.graphics.printf('Welcome to Pong!', 0, 10, VIRTUAL_WIDTH, 'center')
        love.graphics.printf('Press Enter to begin!', 0, 20, VIRTUAL_WIDTH, 'center')
    elseif gameState == 'serve' then
        love.graphics.setFont(smallFont)
        love.graphics.printf('Player ' .. tostring(servingPlayer) .. "'s serve!",
            0, 10, VIRTUAL_WIDTH, 'center')
        love.graphics.printf('Press Enter to serve!', 0, 20, VIRTUAL_WIDTH, 'center')
    elseif gameState == 'play' then
        -- no UI messages to display in play
    end

    player1:render()
    player2:render()
    ball:render()

    displayFPS()

    push:apply('end')
end





10

增加winning condition.

source code

当赢了的时候.

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if player1Score == 10 then
  winningPlayer = 1
  gameState = 'done'
else
  gameState = 'serve'
  ball:reset()
end

当进入下一轮的时候.

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function love.keypressed(key)

    if key == 'escape' then
        love.event.quit()
    -- if we press enter during either the start or serve phase, it should
    -- transition to the next appropriate state
    elseif key == 'enter' or key == 'return' then
        if gameState == 'start' then
            gameState = 'serve'
        elseif gameState == 'serve' then
            gameState = 'play'
        elseif gameState == 'done' then
            -- game is simply in a restart phase here, but will set the serving
            -- player to the opponent of whomever won for fairness!
            gameState = 'serve'

            ball:reset()

            -- reset scores to 0
            player1Score = 0
            player2Score = 0

            -- decide serving player as the opposite of who won
            if winningPlayer == 1 then
                servingPlayer = 2
            else
                servingPlayer = 1
            end
        end
    end
end



11

加音乐!

function

love.audio.newSource(path, [type])

  • Creates a LÖVE2D Audio object that we can play back at any point in our program. Can also be given a “type” of “stream” or “static”; streamed assets will be streamed from disk as needed, whereas static assets will be preserved in memory. For larger sound effects and music tracks, streaming is more memory-effective; in our examples, audio assets are static, since they’re so small that they won’t take up much memory at all.

software

  • Simple sound-generating program, freely available on major OSes.
  • Used to generate all sound effects for our Pong example and most examples going forward.
  • https://www.bfxr.net/

source code

Import sound as a table.

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-- set up our sound effects; later, we can just index this table and
-- call each entry's `play` method
sounds = {
    ['paddle_hit'] = love.audio.newSource('sounds/paddle_hit.wav', 'static'),
    -- if static, it will load into and memory, if steam, they are loaded on the fly
    -- steam is helpful for saving memory(for example large music files)
    ['score'] = love.audio.newSource('sounds/score.wav', 'static'),
    ['wall_hit'] = love.audio.newSource('sounds/wall_hit.wav', 'static')
}

需要的时候.

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sounds['paddle_hit']:play()



12

The Resize Update.

function

love.resize(width, height)

  • Called by LÖVE every time we resize the application; logic should go in here if anything in the game (like a UI) is sized dynamically based on the window size. push:resize() needs to be called here for our use case so that it can dynamically rescale its internal canvas to fit our new window dimensions.

source code

这是最后的版本了,所以是全部的main.lua .

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--[[
    GD50 2018
    Pong Remake

    -- Main Program --

    Author: Colton Ogden
    cogden@cs50.harvard.edu

    Originally programmed by Atari in 1972. Features two
    paddles, controlled by players, with the goal of getting
    the ball past your opponent's edge. First to 10 points wins.

    This version is built to more closely resemble the NES than
    the original Pong machines or the Atari 2600 in terms of
    resolution, though in widescreen (16:9) so it looks nicer on
    modern systems.
]]

-- push is a library that will allow us to draw our game at a virtual
-- resolution, instead of however large our window is; used to provide
-- a more retro aesthetic
--
-- https://github.com/Ulydev/push
push = require 'push'

-- the "Class" library we're using will allow us to represent anything in
-- our game as code, rather than keeping track of many disparate variables and
-- methods
--
-- https://github.com/vrld/hump/blob/master/class.lua
Class = require 'class'

-- our Paddle class, which stores position and dimensions for each Paddle
-- and the logic for rendering them
require 'Paddle'

-- our Ball class, which isn't much different than a Paddle structure-wise
-- but which will mechanically function very differently
require 'Ball'

-- size of our actual window
WINDOW_WIDTH = 1280
WINDOW_HEIGHT = 720

-- size we're trying to emulate with push
VIRTUAL_WIDTH = 432
VIRTUAL_HEIGHT = 243

-- paddle movement speed
PADDLE_SPEED = 200

--[[
    Called just once at the beginning of the game; used to set up
    game objects, variables, etc. and prepare the game world.
]]
function love.load()
    -- set love's default filter to "nearest-neighbor", which essentially
    -- means there will be no filtering of pixels (blurriness), which is
    -- important for a nice crisp, 2D look
    love.graphics.setDefaultFilter('nearest', 'nearest')

    -- set the title of our application window
    love.window.setTitle('Pong')

    -- seed the RNG so that calls to random are always random
    math.randomseed(os.time())

    -- initialize our nice-looking retro text fonts
    smallFont = love.graphics.newFont('font.ttf', 8)
    largeFont = love.graphics.newFont('font.ttf', 16)
    scoreFont = love.graphics.newFont('font.ttf', 32)
    love.graphics.setFont(smallFont)

    -- set up our sound effects; later, we can just index this table and
    -- call each entry's `play` method
    sounds = {
        ['paddle_hit'] = love.audio.newSource('sounds/paddle_hit.wav', 'static'),
        ['score'] = love.audio.newSource('sounds/score.wav', 'static'),
        ['wall_hit'] = love.audio.newSource('sounds/wall_hit.wav', 'static')
    }

    -- initialize our virtual resolution, which will be rendered within our
    -- actual window no matter its dimensions
    push:setupScreen(VIRTUAL_WIDTH, VIRTUAL_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT, {
        fullscreen = false,
        resizable = true,
        vsync = true,
        canvas = false
    })

    -- initialize our player paddles; make them global so that they can be
    -- detected by other functions and modules
    player1 = Paddle(10, 30, 5, 20)
    player2 = Paddle(VIRTUAL_WIDTH - 10, VIRTUAL_HEIGHT - 30, 5, 20)

    -- place a ball in the middle of the screen
    ball = Ball(VIRTUAL_WIDTH / 2 - 2, VIRTUAL_HEIGHT / 2 - 2, 4, 4)

    -- initialize score variables
    player1Score = 0
    player2Score = 0

    -- either going to be 1 or 2; whomever is scored on gets to serve the
    -- following turn
    servingPlayer = 1

    -- player who won the game; not set to a proper value until we reach
    -- that state in the game
    winningPlayer = 0

    -- the state of our game; can be any of the following:
    -- 1. 'start' (the beginning of the game, before first serve)
    -- 2. 'serve' (waiting on a key press to serve the ball)
    -- 3. 'play' (the ball is in play, bouncing between paddles)
    -- 4. 'done' (the game is over, with a victor, ready for restart)
    gameState = 'start'
end

--[[
    Called whenever we change the dimensions of our window, as by dragging
    out its bottom corner, for example. In this case, we only need to worry
    about calling out to `push` to handle the resizing. Takes in a `w` and
    `h` variable representing width and height, respectively.
]]
function love.resize(w, h)
    push:resize(w, h)
end

--[[
    Called every frame, passing in `dt` since the last frame. `dt`
    is short for `deltaTime` and is measured in seconds. Multiplying
    this by any changes we wish to make in our game will allow our
    game to perform consistently across all hardware; otherwise, any
    changes we make will be applied as fast as possible and will vary
    across system hardware.
]]
function love.update(dt)
    if gameState == 'serve' then
        -- before switching to play, initialize ball's velocity based
        -- on player who last scored
        ball.dy = math.random(-50, 50)
        if servingPlayer == 1 then
            ball.dx = math.random(140, 200)
        else
            ball.dx = -math.random(140, 200)
        end
    elseif gameState == 'play' then
        -- detect ball collision with paddles, reversing dx if true and
        -- slightly increasing it, then altering the dy based on the position
        -- at which it collided, then playing a sound effect
        if ball:collides(player1) then
            ball.dx = -ball.dx * 1.03
            ball.x = player1.x + 5

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end

            sounds['paddle_hit']:play()
        end
        if ball:collides(player2) then
            ball.dx = -ball.dx * 1.03
            ball.x = player2.x - 4

            -- keep velocity going in the same direction, but randomize it
            if ball.dy < 0 then
                ball.dy = -math.random(10, 150)
            else
                ball.dy = math.random(10, 150)
            end

            sounds['paddle_hit']:play()
        end

        -- detect upper and lower screen boundary collision, playing a sound
        -- effect and reversing dy if true
        if ball.y <= 0 then
            ball.y = 0
            ball.dy = -ball.dy
            sounds['wall_hit']:play()
        end

        -- -4 to account for the ball's size
        if ball.y >= VIRTUAL_HEIGHT - 4 then
            ball.y = VIRTUAL_HEIGHT - 4
            ball.dy = -ball.dy
            sounds['wall_hit']:play()
        end

        -- if we reach the left or right edge of the screen, go back to serve
        -- and update the score and serving player
        if ball.x < 0 then
            servingPlayer = 1
            player2Score = player2Score + 1
            sounds['score']:play()

            -- if we've reached a score of 10, the game is over; set the
            -- state to done so we can show the victory message
            if player2Score == 10 then
                winningPlayer = 2
                gameState = 'done'
            else
                gameState = 'serve'
                -- places the ball in the middle of the screen, no velocity
                ball:reset()
            end
        end

        if ball.x > VIRTUAL_WIDTH then
            servingPlayer = 2
            player1Score = player1Score + 1
            sounds['score']:play()

            if player1Score == 10 then
                winningPlayer = 1
                gameState = 'done'
            else
                gameState = 'serve'
                ball:reset()
            end
        end
    end

    --
    -- paddles can move no matter what state we're in
    --
    -- player 1
    if love.keyboard.isDown('w') then
        player1.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('s') then
        player1.dy = PADDLE_SPEED
    else
        player1.dy = 0
    end

    -- player 2
    if love.keyboard.isDown('up') then
        player2.dy = -PADDLE_SPEED
    elseif love.keyboard.isDown('down') then
        player2.dy = PADDLE_SPEED
    else
        player2.dy = 0
    end

    -- update our ball based on its DX and DY only if we're in play state;
    -- scale the velocity by dt so movement is framerate-independent
    if gameState == 'play' then
        ball:update(dt)
    end

    player1:update(dt)
    player2:update(dt)
end

--[[
    A callback that processes key strokes as they happen, just the once.
    Does not account for keys that are held down, which is handled by a
    separate function (`love.keyboard.isDown`). Useful for when we want
    things to happen right away, just once, like when we want to quit.
]]
function love.keypressed(key)
    -- `key` will be whatever key this callback detected as pressed
    if key == 'escape' then
        -- the function LÖVE2D uses to quit the application
        love.event.quit()
    -- if we press enter during either the start or serve phase, it should
    -- transition to the next appropriate state
    elseif key == 'enter' or key == 'return' then
        if gameState == 'start' then
            gameState = 'serve'
        elseif gameState == 'serve' then
            gameState = 'play'
        elseif gameState == 'done' then
            -- game is simply in a restart phase here, but will set the serving
            -- player to the opponent of whomever won for fairness!
            gameState = 'serve'

            ball:reset()

            -- reset scores to 0
            player1Score = 0
            player2Score = 0

            -- decide serving player as the opposite of who won
            if winningPlayer == 1 then
                servingPlayer = 2
            else
                servingPlayer = 1
            end
        end
    end
end

--[[
    Called each frame after update; is responsible simply for
    drawing all of our game objects and more to the screen.
]]
function love.draw()
    -- begin drawing with push, in our virtual resolution
    push:start()

    love.graphics.clear(40/255, 45/255, 52/255, 255/255)

    -- render different things depending on which part of the game we're in
    if gameState == 'start' then
        -- UI messages
        love.graphics.setFont(smallFont)
        love.graphics.printf('Welcome to Pong!', 0, 10, VIRTUAL_WIDTH, 'center')
        love.graphics.printf('Press Enter to begin!', 0, 20, VIRTUAL_WIDTH, 'center')
    elseif gameState == 'serve' then
        -- UI messages
        love.graphics.setFont(smallFont)
        love.graphics.printf('Player ' .. tostring(servingPlayer) .. "'s serve!",
            0, 10, VIRTUAL_WIDTH, 'center')
        love.graphics.printf('Press Enter to serve!', 0, 20, VIRTUAL_WIDTH, 'center')
    elseif gameState == 'play' then
        -- no UI messages to display in play
    elseif gameState == 'done' then
        -- UI messages
        love.graphics.setFont(largeFont)
        love.graphics.printf('Player ' .. tostring(winningPlayer) .. ' wins!',
            0, 10, VIRTUAL_WIDTH, 'center')
        love.graphics.setFont(smallFont)
        love.graphics.printf('Press Enter to restart!', 0, 30, VIRTUAL_WIDTH, 'center')
    end

    -- show the score before ball is rendered so it can move over the text
    displayScore()

    player1:render()
    player2:render()
    ball:render()

    -- display FPS for debugging; simply comment out to remove
    displayFPS()

    -- end our drawing to push
    push:finish()
end

--[[
    Simple function for rendering the scores.
]]
function displayScore()
    -- score display
    love.graphics.setFont(scoreFont)
    love.graphics.print(tostring(player1Score), VIRTUAL_WIDTH / 2 - 50,
        VIRTUAL_HEIGHT / 3)
    love.graphics.print(tostring(player2Score), VIRTUAL_WIDTH / 2 + 30,
        VIRTUAL_HEIGHT / 3)
end

--[[
    Renders the current FPS.
]]
function displayFPS()
    -- simple FPS display across all states
    love.graphics.setFont(smallFont)
    love.graphics.setColor(0, 255/255, 0, 255/255)
    love.graphics.print('FPS: ' .. tostring(love.timer.getFPS()), 10, 10)
    love.graphics.setColor(255, 255, 255, 255)
end




Encore

这个project的作业是给paddle1或2加入一个AI.
仔细一读,不需要从头开始code起,只要个feature就行,真是温柔呢.

Implement an AI-controlled paddle (either the left or the right will do) such that it will try to deflect the ball at all times. Since the paddle can move on only one axis (the Y axis), you will need to determine how to keep the paddle moving in relation to the ball. Currently, each paddle has its own chunk of code where input is detected by the keyboard; this feels like an excellent place to put the code we need! Once either the left or right paddle (or both, if desired) try to deflect the paddle on their own, you’ve done it!

At the time of the course’s lectures being filmed, we were using a now-outdated version of LÖVE (0.10.2); most of everything has remained the same into the newer version 11 series of the framework, but one core change is worth noting: love.graphics.clear and functions like it which take four arguments representing the red, green, blue, and alpha components of a color (or RGBA) formerly took integer values between 0 and 255:

love.graphics.clear(255, 0, 0, 255)
However, the API has now changed to where all functions that formerly took integer values for color components now take a floating-point value between 0 and 1; for example, the above API call would translate to the following:

love.graphics.clear(1, 0, 0, 1)
An easy way to normalize the old style to the new style is simply to divide components by 255. If, for example, we had a color we liked with the components 120, 30, 70, and 255, we could write it like the below:

love.graphics.clear(120/255, 30/255, 70/255, 255/255)