function love.load()
	math.randomseed(os.time())
	game = {}
	game.width = 800
	game.height = 480
	game.play = true
	game.score = 0
	game.time_restart = 2
	love.window.setMode(game.width, game.height)
	score = { x = 500, y = 40 }
	-- Background
	background = {}
	background.img = love.graphics.newImage('assets/sprites/background.jpg')
	background.x = 0
	background.y = 0
	-- Spaceship
	spaceship = {}
	spaceship.img = love.graphics.newImage('assets/sprites/spaceship.png')
	spaceship.x = game.height / 8
	spaceship.num_frames = 4
	spaceship.pos_frame = 1
  	spaceship.frame_height = spaceship.img:getHeight() / spaceship.num_frames
	spaceship.y = {
		(game.height / 4) - (spaceship.img:getHeight() / 8),	
		2 * (game.height / 4) - (spaceship.img:getHeight() / 8),	
		3 * (game.height / 4) - (spaceship.img:getHeight() / 8),	
	}
	spaceship.pos = 2
	spaceship.frames = {
                 love.graphics.newQuad(0, spaceship.frame_height * 0, spaceship.img:getWidth(), spaceship.frame_height, spaceship.img:getWidth(), spaceship.img:getHeight()),
                 love.graphics.newQuad(0, spaceship.frame_height * 1, spaceship.img:getWidth(), spaceship.frame_height, spaceship.img:getWidth(), spaceship.img:getHeight()),
                 love.graphics.newQuad(0, spaceship.frame_height * 2, spaceship.img:getWidth(), spaceship.frame_height, spaceship.img:getWidth(), spaceship.img:getHeight()),
                 love.graphics.newQuad(0, spaceship.frame_height * 3, spaceship.img:getWidth(), spaceship.frame_height, spaceship.img:getWidth(), spaceship.img:getHeight())
             }
	-- Asteroids
	num_asteroids = 3
	asteroids = {}
	for i = 1, num_asteroids do
		asteroid = {}
		asteroid.img = love.graphics.newImage('assets/sprites/asteroid_' .. tostring(math.random(1, 9)) .. '.png')
		asteroid.x = game.width
		asteroid.y = {
			(game.height / 4) - (asteroid.img:getHeight() / 2),	
			2 * (game.height / 4) - (asteroid.img:getHeight() / 2),	
			3 * (game.height / 4) - (asteroid.img:getHeight() / 2),	
		}
		asteroid.pos = 2
		asteroid.speed = 600
		asteroids[i] = asteroid
	end
	-- Explosion
        explosion = {}
	explosion.img = love.graphics.newImage('assets/sprites/explosion.png')
	explosion.x = 0
	explosion.y = 0
	explosion.num_frames = 12
	explosion.pos_frame = 1
        explosion.animate = false
  	explosion.frame_width = explosion.img:getWidth() / explosion.num_frames
  	explosion.frame_height = explosion.img:getHeight()
	explosion.frames = {}
	for i = 1, explosion.num_frames do
            explosion.frames[i] = love.graphics.newQuad(explosion.frame_width * (i - 1), 0, explosion.frame_width, explosion.frame_height, explosion.img:getWidth(), explosion.img:getHeight())
        end
	-- Sounds
	sounds = {}
	sounds.die = love.audio.newSource('assets/sounds/die.wav', 'static')	
	sounds.ambient = love.audio.newSource('assets/sounds/ambient.wav', 'static')
	sounds.ambient:play()
	sounds.ambient:setLooping(true)
end

local my_time_restart = 0
function love.update(dt)
	-- Score
	if game.play then
		game.score = game.score + dt * 100
	end
	-- Sprite spaceship
	if spaceship.pos_frame ~= spaceship.num_frames then
		spaceship.pos_frame = spaceship.pos_frame + 1
	else
		spaceship.pos_frame = 1
	end
	-- Asteroids
        if game.play then
            for key, asteroid in pairs(asteroids) do
                asteroid.x = asteroid.x - (dt * asteroid.speed)
                if asteroid.x < -asteroid.img:getWidth() then
                        asteroid.x = game.width + math.random(0, game.width)
                        asteroid.pos = math.random(1, 3)
                end
                -- Colision
                if checkCollision(spaceship.x, spaceship.y[spaceship.pos], spaceship.img:getWidth(), spaceship.img:getHeight() / spaceship.num_frames / 2, asteroid.x, asteroid.y[asteroid.pos], asteroid.img:getWidth(), asteroid.img:getHeight()) then
                        game.play = false
                        sounds.die:play()
                        explosion.animate = true
                        explosion.x = spaceship.x
                        explosion.y = spaceship.y[spaceship.pos]
                end
            end
	end
        -- Sprite explosion
	if explosion.animate and explosion.pos_frame < explosion.num_frames then
		explosion.pos_frame = explosion.pos_frame + 1
        end
	if explosion.pos_frame == explosion.num_frames then
		explosion.pos_frame = 1
                explosion.animate = false
                -- Restart game
                if not game.play then
                        game.play = true
                        game.score = 0
                        my_time_restart = 0
                        for key, asteroid in pairs(asteroids) do
                            asteroid.x = game.width + math.random(0, game.width)
                        end
                end
	end
end

function love.draw()
	-- Background
	love.graphics.draw(background.img, background.x, background.y)
	-- Spaceship
	if game.play then
		love.graphics.draw(spaceship.img, spaceship.frames[spaceship.pos_frame], spaceship.x, spaceship.y[spaceship.pos])
	end
	-- Asteroids
	for key, asteroid in pairs(asteroids) do
		love.graphics.draw(asteroid.img, asteroid.x, asteroid.y[asteroid.pos])
	end
	-- Score
	love.graphics.print('Score: ' .. math.ceil(game.score), score.x , score.y)
	if not game.play then
		love.graphics.print('Game over', game.width / 2, game.height / 2)
	end
        -- Explosion
	love.graphics.draw(explosion.img, explosion.frames[explosion.pos_frame], explosion.x, explosion.y)
end

-- Controls
function love.keypressed(key, scancode, isrepeat)
	if key == 'escape' then
		love.event.push('quit')
	end
	if key == 'up' and spaceship.pos > 1 then
		spaceship.pos = spaceship.pos - 1
	elseif key == 'down' and spaceship.pos < 3 then
		spaceship.pos = spaceship.pos + 1
	end
end

function checkCollision(x1,y1,w1,h1, x2,y2,w2,h2)
  return x1 < x2 + w2 and
         x2 < x1 + w1 and
         y1 < y2 + h2 and
         y2 < y1 + h1
end