FlappyTurtle/Bird.java

public class Bird
{
    private static final int GRAVITY = 20;
    private static final int JUMP_SPEED = 7;
    private final Rectangle _rect;
    private double _speed;

    public Bird(GameScreen game)
    {
        _rect = new Rectangle(20, 20, 20, 20, "cyan", true);
        game.addDrawable(_rect);
    }

    public void reset()
    {
        _rect.setPos(20, 20);
        _speed = 0;
    }

    public void update(double elapsed)
    {
        _speed += GRAVITY * elapsed * 1e-3d;
        _rect.setPos(_rect.getX(), _rect.getY() + _speed);
    }

    public void jump()
    {
        _speed = -JUMP_SPEED;
    }

    public Rectangle getRect()
    {
        return _rect;
    }
}