Breakout in Greenfoot

1. Breakout in Greenfoot Barb Ericson Georgia Institute of Technology June 2007 Georgia Institute of Technology

2. The Breakout Game • Open Breakout-Start • There are Bricks, a Message that says we are starting with Ball 1, a Ball, and a Paddle • But if you click on act or run nothing happens Georgia Institute of Technology

3. Game Rules • Use the left and right arrow keys to move the paddle • Use the paddle to hit the ball into the bricks to get rid of them • Get rid of all the bricks to win the game • The ball will bounce off most of the walls, paddle, and bricks • You get up to three balls to use • If you still have bricks after using 3 balls you lose • If a ball hits the bottom wall it is removed and new ball added Georgia Institute of Technology

4. Moving the Paddle • Check if the left key is down • Greenfoot.isKeyDown("left") • if it is move left • setLocation(getX() – moveAmount, y); • else check if the right key is down • Greenfoot.isKeyDown("right") • if it is move right • setLocation(getX() + moveAmount,y); Georgia Institute of Technology

5. The Ball's Act Method • Move the ball • Check if hit any actors • If hit an actor and that actor isn't the message • Bounce off the object • Check if the object was a brick • if it was a brick remove the brick from the world and have the world check if the player won (no more bricks) • Check if at any walls • Bounce off top or side walls • If at bottom wall remove ball and create a new one Georgia Institute of Technology

6. Move the Ball • The ball's y velocity is 3 but is a field • velY • The ball's x velocity should be a random value between 1 and 3 or -1 to -3 • set in the constructor • velX • To move the ball • add velX to the current x (getX) • add velY to the current y (getY) • Use setLocation(x,y); Georgia Institute of Technology

7. Checking if hit any Actors • Get an actor (object of the class Actor) that intersects with this one Actor actor = this.getOneIntersectingObject(Actor.class); • If the ball did hit an actor and it isn't the message (object of the Message class) • if (actor != null && !(actor instanceof Message)) Georgia Institute of Technology

8. Bounce the Ball off an Actor • The actor must be a paddle or a brick (if it isn't a message) • So negate velY velY = -velY; Georgia Institute of Technology

9. If the Ball hit a Brick • Check using • if (actor instanceof Brick) • If the ball did hit a brick • remove it • world.removeObject(actor); • check if won • world.checkIfWon(); Georgia Institute of Technology

10. Checking Walls • If the ball hit the left wall • if (getX() - radius <= 0) • negate velX • else If the ball hit the right wall • if (getX() + radius >= BreakoutWorld.WIDTH) • negate velX • else If the ball hit the top wall • else if (getY() - radius <= 0) • negate velY Georgia Institute of Technology

11. Checking Bottom Wall • else if (getY() + radius >= BreakoutWorld.HEIGHT) • remove the current ball from the world • world.removeObject(this); • add a new ball to the world • world.newBall(); • this also checks for the end of the game Georgia Institute of Technology

12. Additional Ideas • Add sounds • bounce sound and win or lose sounds • If hit at edge of paddle then bounce in x as well as y • Speed up the velocity • after each 7th hit • double the x velocity • See the documentation for the Greenfoot classes • http://www.greenfoot.org/doc/javadoc/ Georgia Institute of Technology