Breakout in Greenfoot

1. Breakout in Greenfoot Barb Ericson ericson@cc.gatech.edu Georgia Institute of Technology Feb 2010 Breakout

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 Breakout

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 a new ball is added Breakout

4. Moving the Paddle (act method) • Check if the left key is down if (Greenfoot.isKeyDown("left")) • if it is move the paddle left setLocation(getX()-moveAmount, getY()); • Check if the right key is down if (Greenfoot.isKeyDown("right")) • if it is move the paddle right setLocation(getX()+moveAmount, getY()); Breakout

5. The Ball's Act Method • Move the ball • Set the location using the current x and y and velX and velY (amount to move in X and Y) • 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 Breakout

6. Move the Ball • The ball's y velocity is 3, but it 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 setLocation(getX() + velX, getY() + velY); Breakout

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

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 to make it switch direction in Y velY = -velY; Breakout

9. If the Ball hit a Brick • Check using if (actor instanceof Brick) { • If the ball did hit a brick • remove the brick from the world world.removeObject(actor); • check if won (last brick was removed) world.checkIfWon(); } } Breakout

10. Checking Walls • If the ball hit the left wall bounce in x if (getX() - radius <= 0) velX = -velX; // negate velocity in X • if the ball hit the right wall bounce in x if (getX() + radius >= BreakoutWorld.WIDTH) velX = -velX; // negate velocity in X • if the ball hit the top wall bounce in y else if (getY() - radius <= 0) velY = -velY; // negate velocity in Y Breakout

11. Checking Bottom Wall 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 } Breakout

12. Additional Ideas • Add sounds • bounce sound and win or lose sounds • If the ball hits at the edge of paddle then bounce in x as well as y • if the distance from the center of the ball to the left or right edge of the paddle is less than or equal the radius of the ball • Speed up the velocity • after each 7th hit with the paddle • double the x velocity • Make the paddle smaller over time • Change the ball color to match the last hit brick's color • Add a getColor() method to Brick • See the documentation for the Greenfoot classes • http://www.greenfoot.org/doc/javadoc/ Breakout

13. Ideas for Breakout • Introduce object-oriented analysis using Breakout-export • Have them name the classes shown and describe the methods needed • Give students Breakout-Start • Have them create the full code for Breakout Breakout