Ball.lua

require 'Paddle'
Ball = class()
BALL_XSPPED = 150

function Ball:init(width, height)
	self.x = VIRTUAL_WIDTH / 2 - BALL_SIZE / 2
	self.y = VIRTUAL_HEIGHT / 2 - BALL_SIZE / 2
	self.width = width
	self.height = height

	self.dx = math.random(2) == 1 and BALL_XSPPED or -BALL_XSPPED
	self.dy = math.random(-50, 50)
end

function Ball:reset()
	self.x = VIRTUAL_WIDTH / 2 - BALL_SIZE / 2
	self.y = VIRTUAL_HEIGHT / 2 - BALL_SIZE / 2
	self.dx = math.random(2) == 1 and BALL_XSPPED or -BALL_XSPPED
	self.dy = math.random(-50, 50)
end

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

function Ball:update(dt)
       self.x = self.x + dt * self.dx
       self.y = self.y + dt * self.dy
end

function Ball:collide(Paddle)
	if self.x > Paddle.x + 3 or Paddle.x > self.x + 4 then
		-- no collision occur
		return false
	end
	if self.y > Paddle.y + PADDLE_HEIGHT or self.y + 4 < Paddle.y then
		-- need to add marks to next player
		return false
	end
	-- collision occur, need to update the ball movement
	return true
end