local playerx = 10
local playery = 10
local angle = 0

local playerspeed = 0
local playerswspeed = 0
local playermaxspeed = 100

function love.update(dt)
	local mousex, mousey =  love.mouse.getPosition()
	angle = -(mousex / love.graphics.getWidth()) + 0.5
	playerx = playerx + math.sin(angle) * playerspeed * dt
	playerx = playerx + math.cos(angle) * playerswspeed * dt
	playery = playery + math.cos(angle) * playerspeed * dt
	playery = playery - math.sin(angle) * playerswspeed * dt
end

function love.keypressed(key)
	if key == 'w' then
		playerspeed = playerspeed + playermaxspeed
	elseif key == 's' then
		playerspeed = playerspeed - playermaxspeed
	elseif key == 'a' then
		playerswspeed = playerswspeed + playermaxspeed
	elseif key == 'd' then
		playerswspeed = playerswspeed - playermaxspeed
	end
end

function love.keyreleased(key)
	if key == 'w' then
		playerspeed = playerspeed - playermaxspeed
	elseif key == 's' then
		playerspeed = playerspeed + playermaxspeed
	elseif key == 'a' then
		playerswspeed = playerswspeed - playermaxspeed
	elseif key == 'd' then
		playerswspeed = playerswspeed + playermaxspeed
	end
end

local fov = 90 * math.pi / 180

function transform(wx, wy)
	-- Player-relative space (translation)
	local tx = wx - playerx
	local ty = wy - playery

	-- Player-relative space (rotation)
	local rx = math.cos(angle) * tx - math.sin(angle) * ty
	local ry = math.cos(angle) * ty + math.sin(angle) * tx

	-- -1.0 to +1.0 abstract screen space (perspective)
	-- Player-relative x maps to *-x*
	-- Player-relative y maps to *z*
	local px = -rx / ry / math.tan(fov / 2)
	local pz = ry

	-- Screen space (scaling and translation)
	local hwidth = love.graphics.getWidth() / 2
	local x = px * hwidth + hwidth

	return x, pz
end

function drawWall(wx1, wy1, wx2, wy2)
	local hwidth = love.graphics.getWidth() / 2
	local hheight = love.graphics.getHeight() / 2
	love.graphics.setColor(255, 0, 0)
	love.graphics.line(wx1 + hwidth, wy1 + hheight, wx2 + hwidth, wy2 + hheight)

	local x1, z1 = transform(wx1, wy1)
	local x2, z2 = transform(wx2, wy2)

	love.graphics.setColor(255, 255, 255)
	love.graphics.line(x1, hheight - 60 * hheight / z1 / math.tan(fov / 2), x2, hheight - 60 * hheight / z2 / math.tan(fov / 2))
	love.graphics.line(x1, hheight + 60 * hheight / z1, x2, hheight + 60 * hheight / z2)
end

function love.draw()
	local hwidth = love.graphics.getWidth() / 2
	local hheight = love.graphics.getHeight() / 2

	drawWall(-300, 100, 300, 100)

	drawWall(playerx, playery, playerx + math.sin(angle) * 5, playery + math.cos(angle) * 5)
end