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

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 Give your students the Breakout-Start and Breakout-export folders. The complete game is in Breakout. Breakout

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 Use the exported applet of Breakout to show them the final game working. Breakout

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()); moveAmount is a field in Paddle. Breakout

The Ball's Act Method Move the ball Check if hit any actors 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

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

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

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

If the Ball hit a Brick Check using If the ball did hit a brick 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

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) if the ball hit the top wall bounce in y else if (getY() - radius <= 0) velY = -velY; // negate velocity in Y Breakout

Checking Bottom Wall remove the current ball from the world 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

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

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