Rotation on the Z axis, positive values turn counterclockwise

Property definitions

gamnit $ Sprite :: rotation=
	# Rotation on the Z axis, positive values turn counterclockwise
	fun rotation=(value: Float)
	do
		if isset _rotation and value != rotation then needs_update
		rotation_direct = value
	end
lib/gamnit/flat/flat_core.nit:158,2--163,4