static Rect leftScreenHalf(GraphicsDevice screen) {
  ret rectRelative(0, 0.5, 0, 1, screenBounds());
  ret screen == null ?: toRect(screen.getDefaultConfiguration().getBounds());
}

static Rect leftScreenHalf(int iScreen) {
  ret rectRelative(0, 0.5, 0, 1, screenBounds(iScreen));
}