if (isLeftButtonDown) {
surface.setStrokeStyle(KnownColor.BLACK).setLineWidth(5);
} else if (isRightButtonDown) {
surface.setStrokeStyle(KnownColor.WHITE).setLineWidth(20);
}
surface.strokeShape(new ShapeBuilder()
.drawLineSegment(lastPosition, new Vector2(event.getX(), event.getY()))
.build());
surface.restore();
lastPosition.set(event.getX(), event.getY());
}