snake.lua

segmentImage = Image.load("segment.png")
pi = 4*math.atan(1)
green = Color.new(0,255,0)
black = Color.new(0,0,0)
segmentSize = segmentImage:width()
segmentSpace = segmentSize - 2
width = 480 + 2 * segmentSize
height = 272 + 2 * segmentSize

function init()
	x = 100
	head = { dir = 0, posX = x, posY = 100, next = nil }
	for i=1,20 do
		x = x + segmentSpace
		head = { dir = 0, posX = x, posY = 100, next = head }
	end
	dir = 0
end

function drawSegment(seg)
	screen:blit(seg.posX, seg.posY, segmentImage)
end

function adjustSegment(seg)
	if seg.posX < -segmentSize then seg.posX = seg.posX + width end
	if seg.posX > width-segmentSize then seg.posX = seg.posX - width end
	if seg.posY < -segmentSize then seg.posY = seg.posY + height end
	if seg.posY > height-segmentSize then seg.posY = seg.posY - height end
end

function drawSnake(head, dir)
	drawSegment(head)
	head.posX = head.posX + math.sin(dir) * 2
	head.posY = head.posY + math.cos(dir) * 2
	adjustSegment(head)
	seg = head.next
	lastX = head.posX
	lastY = head.posY
	while seg do
		drawSegment(seg)
		dx = lastX - seg.posX
		dy = lastY - seg.posY
		if dx < -240 then dx = dx + width end
		if dy < -136 then dy = dy + height end
		if dx > 240 then dx = dx - width end
		if dy > 136 then dy = dy - height end
        	r = math.atan2(dx, dy)
        	lastX = lastX - math.sin(r) * segmentSpace
        	lastY = lastY - math.cos(r) * segmentSpace
        	seg.posX = lastX
        	seg.posY = lastY
        	adjustSegment(seg)
        	seg = seg.next
        end
end

init()
timer = Timer.new()
fps = 0
fpsUpdate = 0
while true do
	if fpsUpdate == 9 then
		fpsUpdate = 0
		fps = math.floor(10000 / timer:time() + 0.5)
		timer:reset()
		timer:start()
	else
		fpsUpdate = fpsUpdate + 1
	end
	controls = Controls.read() 
	if controls:start() then break end
	screen:clear(black)
	dx = controls:analogX()
	dy = controls:analogY()
	if dx*dx + dy*dy > 200 then
		dir = math.atan2(dx, dy)
	end
	drawSnake(head, dir)
	screen:print(0, 0, "fps: " .. tostring(fps), green)
	screen.waitVblankStart()
	screen.flip()
end