Shape transformer experiment using LÖVE

main.lua

local x, y = 400, 300
local lineLength = 150
local rotationChange = -0.003

function rotateAround(x1, y1, x2, y2, r)
	local c, s = math.cos(r), math.sin(r)
	return c * (x1 - x2) - s * (y1 - y2) + x2, s * (x1 - x2) + c * (y1 - y2) + y2 -- rotate x1,y1 around x2,y2 by r
end

local c, curR, addR
function love.load()
	c = love.graphics.newCanvas(800, 600)
	curR = 0
	addR = math.pi
	y = y - lineLength / 2
end

function love.draw()
	local curX, curY = x, y
	addR = addR + rotationChange
	curR = curR + addR
	x, y = rotateAround(curX, curY - lineLength, curX, curY, curR)

	love.graphics.setCanvas(c)
	love.graphics.setColor(0, 0, 0, 0.015)
	love.graphics.rectangle("fill", 0, 0, 800, 600)
	love.graphics.setColor(0, 1, 0, 1)

	love.graphics.line(curX, curY, x, y)

	love.graphics.setCanvas(nil)
	love.graphics.draw(c)
end