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

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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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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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)
• negate velX
• 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
– http://www.greenfoot.org/doc/javadoc/
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