(fn dir-from-key [keymap]
  (var (dx dy) (values 0 0))
  (when (love.keyboard.isDown keymap.up)    (set dy -1))
  (when (love.keyboard.isDown keymap.down)  (set dy 1))
  (when (love.keyboard.isDown keymap.left)  (set dx -1))
  (when (love.keyboard.isDown keymap.right) (set dx 1))
  [dx dy])

(fn vec* [vec scalar]
  (icollect [_ v (ipairs vec)] (* v scalar)))

{: dir-from-key : vec*}