// Draw directs each layer, starting from the bottom, to draw to the
// screen, and then updates the necessary parts of the screen.
func (stack LayerStack) Draw(screen *sdl.Surface) {
screen.FillRect(
&sdl.Rect{X: 0, Y: 0, W: uint16(screen.W), H: uint16(screen.H)},
0,
)
for i, layer := range stack {
top := i == len(stack)-1
layer.Draw(screen, top)
}
screen.Flip()
}
