“Hundreds” Flash game prototype using Box2D – handling collisions

January 28, 2013 • Actionscript 3, Box2D, Flash, Game design by Emanuele Feronato • 1 Comment

Welcome to the second part of the Box2D Hundreds prototype.

In this second part I am going to add some features which will make the prototype looking more like the original game, while having something different, just to make a new concept.

So the game now works this way:

* You can make a circle grow endlessly as long as you stay with the mouse over it
* The circle will stop growing, and will never grow again, if you leave the mouse from over it
* If a growing circle hits any other circle, both circles won’t be able to grow anymore and the size of the currently growing circle will be reduced by half.

Give it a try:

This is the commented source code for the main class:

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.*;
	public class Main extends Sprite {
		// world definition
		private var world:b2World=new b2World(new b2Vec2(0,0),true);
		private var worldScale:Number=30;
		// custom contact listener
		private var customContact=new CustomContactListener();
		// speed of circles
		private var circleSpeed:Number=5;
		// body currently being touched
		private var currentBody:b2Body=null;
		// check if the mouse was over something
		private var overSomething:Boolean;
		public function Main() {
			// setting the custom contact listener
			world.SetContactListener(customContact);
			debugDraw();
			// adding 10 random circles
			for (var i:Number=1; i<=10; i++) {
				addCircle();
			}
			// adding boundary walls
			addWall(320,0,640,10);
			addWall(320,480,640,10);
			addWall(0,240,10,480);
			addWall(640,240,10,480);
			addEventListener(Event.ENTER_FRAME,update);
		}
		private function debugDraw():void {
			var debugDraw:b2DebugDraw=new b2DebugDraw();
			var debugSprite:Sprite=new Sprite();
			addChild(debugSprite);
			debugDraw.SetSprite(debugSprite);
			debugDraw.SetDrawScale(worldScale);
			debugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);
			debugDraw.SetFillAlpha(0.5);
			world.SetDebugDraw(debugDraw);
		}
		private function addCircle():void {
			var bodyDef:b2BodyDef= new b2BodyDef();
			bodyDef.type=b2Body.b2_dynamicBody;
			bodyDef.position.Set(Math.round(Math.random()*600+20)/worldScale,Math.round(Math.random()*440+20)/worldScale);
			bodyDef.userData={name:"sphere",canGrow:true,isGroving:false};
			var circleShape:b2CircleShape = new b2CircleShape(10/worldScale);
			var fixtureDef:b2FixtureDef = new b2FixtureDef();
			fixtureDef.density=1;
			fixtureDef.friction=0;
			fixtureDef.restitution=0.5;
			fixtureDef.shape=circleShape;
			var body:b2Body=world.CreateBody(bodyDef);
			body.CreateFixture(fixtureDef);
			// giving the circle a random direction
			var randomAngle:Number=Math.random()*2*Math.PI;
			body.SetLinearVelocity(new b2Vec2(circleSpeed*Math.cos(randomAngle),circleSpeed*Math.sin(randomAngle)));
		}
		private function addWall(pX:Number,pY:Number,w:Number,h:Number):void {
			var bodyDef:b2BodyDef=new b2BodyDef();
			bodyDef.position.Set(pX/worldScale,pY/worldScale);
			var polygonShape:b2PolygonShape=new b2PolygonShape();
			polygonShape.SetAsBox(w/2/worldScale,h/2/worldScale);
			var fixtureDef:b2FixtureDef=new b2FixtureDef();
			fixtureDef.shape=polygonShape;
			fixtureDef.density=1;
			fixtureDef.restitution=0.5;
			fixtureDef.friction=0;
			var theWall:b2Body=world.CreateBody(bodyDef);
			theWall.CreateFixture(fixtureDef);
		}
		// the core of the script, looking for the body touched and 
		// increasing the size of the circle shape
		private function queryCallback(fixture:b2Fixture):Boolean {
			var touchedBody:b2Body=fixture.GetBody();
			if (touchedBody.GetUserData()!=null) {
				overSomething=true;
				if (touchedBody!=currentBody) {
					if (currentBody!=null) {
						currentBody.GetUserData().isGroving=false;
						currentBody.GetUserData().canGrow=false;
					}
					currentBody=touchedBody;
				}
				if (touchedBody.GetUserData().canGrow) {
					touchedBody.GetUserData().isGrowing=true;
					var fixture:b2Fixture=touchedBody.GetFixtureList();
					var circleDef:b2CircleShape=fixture.GetShape() as b2CircleShape;
					var radius:Number=circleDef.GetRadius();
					circleDef.SetRadius(radius+1/worldScale);
				}
			}
			return false;
		}
		private function update(e:Event):void {
			world.Step(1/30,10,10);
			world.ClearForces();
			// checking for bodies under the mouse
			overSomething=false;
			world.QueryPoint(queryCallback,new b2Vec2(mouseX/worldScale,mouseY/worldScale));
			for (var b:b2Body=world.GetBodyList(); b; b=b.GetNext()) {
				if (b.GetUserData()!=null) {
					if (! overSomething&&b.GetUserData().isGrowing) {
						b.GetUserData().isGrowing=false;
						b.GetUserData().canGrow=false;
					}
					// keep moving circles at a constant speed
					var velocity:b2Vec2=b.GetLinearVelocity();
					var speed:Number=velocity.Length();
					var ratio:Number=circleSpeed/speed;
					velocity.Multiply(ratio);
					b.SetLinearVelocity(velocity);
				}
			}
			world.DrawDebugData();
		}
	}
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

package {

import flash.display.Sprite;

import flash.events.Event;

import Box2D.Dynamics.*;

import Box2D.Collision.*;

import Box2D.Collision.Shapes.*;

import Box2D.Common.Math.*;

public class Main extends Sprite {

// world definition

private var world:b2World=new b2World(new b2Vec2(0,0),true);

private var worldScale:Number=30;

// custom contact listener

private var customContact=new CustomContactListener();

// speed of circles

private var circleSpeed:Number=5;

// body currently being touched

private var currentBody:b2Body=null;

// check if the mouse was over something

private var overSomething:Boolean;

public function Main() {

// setting the custom contact listener

world.SetContactListener(customContact);

debugDraw();

// adding 10 random circles

for (var i:Number=1; i<=10; i++) {

addCircle();

}

// adding boundary walls

addWall(320,0,640,10);

addWall(320,480,640,10);

addWall(0,240,10,480);

addWall(640,240,10,480);

addEventListener(Event.ENTER_FRAME,update);

}

private function debugDraw():void {

var debugDraw:b2DebugDraw=new b2DebugDraw();

var debugSprite:Sprite=new Sprite();

addChild(debugSprite);

debugDraw.SetSprite(debugSprite);

debugDraw.SetDrawScale(worldScale);

debugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);

debugDraw.SetFillAlpha(0.5);

world.SetDebugDraw(debugDraw);

}

private function addCircle():void {

var bodyDef:b2BodyDef= new b2BodyDef();

bodyDef.type=b2Body.b2_dynamicBody;

bodyDef.position.Set(Math.round(Math.random()*600+20)/worldScale,Math.round(Math.random()*440+20)/worldScale);

bodyDef.userData={name:"sphere",canGrow:true,isGroving:false};

var circleShape:b2CircleShape = new b2CircleShape(10/worldScale);

var fixtureDef:b2FixtureDef = new b2FixtureDef();

fixtureDef.density=1;

fixtureDef.friction=0;

fixtureDef.restitution=0.5;

fixtureDef.shape=circleShape;

var body:b2Body=world.CreateBody(bodyDef);

body.CreateFixture(fixtureDef);

// giving the circle a random direction

var randomAngle:Number=Math.random()*2*Math.PI;

body.SetLinearVelocity(new b2Vec2(circleSpeed*Math.cos(randomAngle),circleSpeed*Math.sin(randomAngle)));

}

private function addWall(pX:Number,pY:Number,w:Number,h:Number):void {

var bodyDef:b2BodyDef=new b2BodyDef();

bodyDef.position.Set(pX/worldScale,pY/worldScale);

var polygonShape:b2PolygonShape=new b2PolygonShape();

polygonShape.SetAsBox(w/2/worldScale,h/2/worldScale);

var fixtureDef:b2FixtureDef=new b2FixtureDef();

fixtureDef.shape=polygonShape;

fixtureDef.density=1;

fixtureDef.restitution=0.5;

fixtureDef.friction=0;

var theWall:b2Body=world.CreateBody(bodyDef);

theWall.CreateFixture(fixtureDef);

}

// the core of the script, looking for the body touched and

// increasing the size of the circle shape

private function queryCallback(fixture:b2Fixture):Boolean {

var touchedBody:b2Body=fixture.GetBody();

if (touchedBody.GetUserData()!=null) {

overSomething=true;

if (touchedBody!=currentBody) {

if (currentBody!=null) {

currentBody.GetUserData().isGroving=false;

currentBody.GetUserData().canGrow=false;

}

currentBody=touchedBody;

}

if (touchedBody.GetUserData().canGrow) {

touchedBody.GetUserData().isGrowing=true;

var fixture:b2Fixture=touchedBody.GetFixtureList();

var circleDef:b2CircleShape=fixture.GetShape() as b2CircleShape;

var radius:Number=circleDef.GetRadius();

circleDef.SetRadius(radius+1/worldScale);

}

return false;

}

private function update(e:Event):void {

world.Step(1/30,10,10);

world.ClearForces();

// checking for bodies under the mouse

overSomething=false;

world.QueryPoint(queryCallback,new b2Vec2(mouseX/worldScale,mouseY/worldScale));

for (var b:b2Body=world.GetBodyList(); b; b=b.GetNext()) {

if (b.GetUserData()!=null) {

if (! overSomething&&b.GetUserData().isGrowing) {

b.GetUserData().isGrowing=false;

b.GetUserData().canGrow=false;

}

// keep moving circles at a constant speed

var velocity:b2Vec2=b.GetLinearVelocity();

var speed:Number=velocity.Length();

var ratio:Number=circleSpeed/speed;

velocity.Multiply(ratio);

b.SetLinearVelocity(velocity);

}

world.DrawDebugData();

}

and for the contact listener:

package {
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Dynamics.Joints.*;
	import Box2D.Dynamics.Contacts.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.b2Vec2;
	class CustomContactListener extends b2ContactListener {
		override public function PreSolve(contact:b2Contact, oldManifold:b2Manifold):void {
			// is the contact touching?
			if (contact.IsTouching()) {
				// getting the bodies involved
				var bodyA:b2Body=contact.GetFixtureA().GetBody();
				var bodyB:b2Body=contact.GetFixtureB().GetBody();
				// retrieving their user data objects
				var objA:Object=bodyA.GetUserData();
				var objB:Object=bodyB.GetUserData();
				var fixture:b2Fixture;
				var circleDef:b2CircleShape;
				var radius:Number;
				if (objA!=null && objB!=null) {
					if (objA.isGrowing) {
						objA.isGroving=false;
						objA.canGrow=false;
						fixture=bodyA.GetFixtureList();
						circleDef=fixture.GetShape() as b2CircleShape;
						radius=circleDef.GetRadius();
						circleDef.SetRadius(radius/2);
					}
					if (objB.isGrowing) {
						objB.isGroving=false;
						objB.canGrow=false;
						fixture=bodyB.GetFixtureList();
						circleDef=fixture.GetShape() as b2CircleShape;
						radius=circleDef.GetRadius();
						circleDef.SetRadius(radius/2);
					}
				}
			}
		}
	}
}

package {

import Box2D.Dynamics.*;

import Box2D.Collision.*;

import Box2D.Dynamics.Joints.*;

import Box2D.Dynamics.Contacts.*;

import Box2D.Collision.Shapes.*;

import Box2D.Common.Math.b2Vec2;

class CustomContactListener extends b2ContactListener {

override public function PreSolve(contact:b2Contact, oldManifold:b2Manifold):void {

// is the contact touching?

if (contact.IsTouching()) {

// getting the bodies involved

var bodyA:b2Body=contact.GetFixtureA().GetBody();

var bodyB:b2Body=contact.GetFixtureB().GetBody();

// retrieving their user data objects

var objA:Object=bodyA.GetUserData();

var objB:Object=bodyB.GetUserData();

var fixture:b2Fixture;

var circleDef:b2CircleShape;

var radius:Number;

if (objA!=null && objB!=null) {

if (objA.isGrowing) {

objA.isGroving=false;

objA.canGrow=false;

fixture=bodyA.GetFixtureList();

circleDef=fixture.GetShape() as b2CircleShape;

radius=circleDef.GetRadius();

circleDef.SetRadius(radius/2);

}

if (objB.isGrowing) {

objB.isGroving=false;

objB.canGrow=false;

fixture=bodyB.GetFixtureList();

circleDef=fixture.GetShape() as b2CircleShape;

radius=circleDef.GetRadius();

circleDef.SetRadius(radius/2);

}

Download the source code. Next time, Nape version.

Rate this post: 1 Star

(6 votes, average: 5.00 out of 5)

Loading ...

Flash Templates provided by Template Monster are pre-made web design products developed using Flash technology.
They can be easily customized to meet the unique requirements of your project.

Be my fan on Facebook and follow me on Twitter! Exclusive content for my Facebook fans and Twitter followers

This post has one comment

Lim Fhiau

on February 2, 2013 at 11:40 am

it’s hard to play this game when using touchpad :D

Emanuele Feronato

italian geek and PROgrammer

“Hundreds” Flash game prototype using Box2D – handling collisions

This post has one comment

Lim Fhiau