1. Barb Ericson Georgia Institute of Technology June 2007
Breakout in Greenfoot
Barb Ericson
Georgia Institute of Technology
June 2007
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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
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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
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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);
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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
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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);
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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))
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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;
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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();
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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)
else If the ball hit the top wall
else if (getY() - radius <= 0)
negate velY
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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
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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
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