fix-to(a, b)
  position fixed
  {a} 0
  {b} 0

.button
  fix-to bottom left


fix-to(pos...)
  position fixed
  if length(pos) == 2
    {pos[0]} 0
    {pos[1]} 0
  else if length(pos) == 4
    a = pos[0..1]
    b = pos[2..3]
    {a[0]} a[1]
    {b[0]} b[1]
  else
    error('invalid arguments. fix-to: <pos> [n] <pos> [n];')
    
.button
  fix-to bottom left

.button
  fix-to bottom 5px left 5px