Rotate.elm

import Window
import Mouse

fpsCount = 35
delta = fps fpsCount
time = foldp (+) 0.0 delta
timeSeconds = (\ x -> x / 1000.0) <~ time

black = rgb 0 0 0
display (w, h) (x, y) t =
  container w h middle <| collage w h
    [ rect 50 50 |>
      filled black |>
      move (toFloat (x - w `div` 2), toFloat (-y + h `div` 2)) |>
      rotate t ]
main = display <~ Window.dimensions ~ Mouse.position ~ timeSeconds