Quick Switch Flash game prototype made with Box2D

Read all posts about "" game

A simple and addictive game which is interesting to deconstruct is Quick Switch. Use your mouse to hover over and activate platforms to guide your ball to the target.

In the making of this prototype, I’ll be using all body types Box2D allows me to use, so we have:

Static Bodies: will be used for platform which are always active

Dynamic Bodies: will be used for the ball

Kinematic Bodies: will be used for platform which need to be activated. If you don’t know what is a kinematic body, read understanding Box2D kinematic bodies.

To simplify the process of level design, I will start from the project basic Box2D editor using Flash movieclips.

So this is the final script:

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.utils.*;
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.*;
	public class Main extends Sprite {
		private var boxOriginalSize:int=40;
		private var editor:Editor = new Editor();
		private var world:b2World=new b2World(new b2Vec2(0,5),true);
		private var worldScale:int=30;
		public function Main():void {
			debugDraw();
			addChild(editor);
			for (var i:int=0; i500/worldScale) {
							b.SetPosition(new b2Vec2(500/worldScale,-50/worldScale));
							b.SetLinearVelocity(new b2Vec2(0,0));
						}
						break;
					case b2Body.b2_kinematicBody :
						for (var f:b2Fixture=b.GetFixtureList(); f; f=f.GetNext()) {
							f.SetSensor(true);
						}
						break;
				}
			}
			world.QueryPoint(queryCallback,new b2Vec2(mouseX/worldScale,mouseY/worldScale));
			world.DrawDebugData();
		}
	}
}

And this is the result:

Hover the mouse over purple platform to make them solid and drive the ball into the green goal.

Now, let’s see the interesting part of this script, which is update function:

private function update(e : Event):void {
	world.Step(1/30,10,10);
	world.ClearForces();
	for (var b:b2Body=world.GetBodyList(); b; b=b.GetNext()) {
		switch (b.GetType()) {
			case b2Body.b2_dynamicBody :
				if (b.GetPosition().y>500/worldScale) {
					b.SetPosition(new b2Vec2(500/worldScale,-50/worldScale));
					b.SetLinearVelocity(new b2Vec2(0,0));
				}
				break;
			case b2Body.b2_kinematicBody :
				for (var f:b2Fixture=b.GetFixtureList(); f; f=f.GetNext()) {
					f.SetSensor(true);
				}
				break;
		}
	}
	world.QueryPoint(queryCallback,new b2Vec2(mouseX/worldScale,mouseY/worldScale));
	world.DrawDebugData();
}

Line 85: looping through all bodies

Line 86: now it’s time to make different things according to body type

Lines 87-92: it’s a dynamic body (the falling ball): I just put it in its starting place if it falls down the stage

Lines 93-97: it’s a kinematic body (an activable platform): I turn it into a sensor. It’s the best thing to do to make it “transparent”. It does not react to collision.

Line 100: Now it’s time to check for mouse position and check for bodies under the mouse with queryCallback function.

private function queryCallback(fixture:b2Fixture):Boolean {
	var touchedBody:b2Body=fixture.GetBody();
	for (var f:b2Fixture=touchedBody.GetFixtureList(); f; f=f.GetNext()) {
		f.SetSensor(false);
	}
	return false;
}

This function simply scans for all fixtures inside the body under the mouse and does not make them sensors anymore.

And that’s it.

Download the source code.

Get the most popular Phaser 3 book

Through 202 pages, 32 source code examples and an Android Studio project you will learn how to build cross platform HTML5 games and create a complete game along the way.

Get the book

215 GAME PROTOTYPES EXPLAINED WITH SOURCE CODE
// 1+2=3
// 100 rounds
// 10000000
// 2 Cars
// 2048
// A Blocky Christmas
// A Jumping Block
// A Life of Logic
// Angry Birds
// Angry Birds Space
// Artillery
// Astro-PANIC!
// Avoider
// Back to Square One
// Ball Game
// Ball vs Ball
// Ball: Revamped
// Balloon Invasion
// BallPusher
// Ballz
// Bar Balance
// Bejeweled
// Biggification
// Block it
// Blockage
// Bloons
// Boids
// Bombuzal
// Boom Dots
// Bouncing Ball
// Bouncing Ball 2
// Bouncy Light
// BoxHead
// Breakout
// Bricks
// Bubble Chaos
// Bubbles 2
// Card Game
// Castle Ramble
// Chronotron
// Circle Chain
// Circle Path
// Circle Race
// Circular endless runner
// Cirplosion
// CLOCKS - The Game
// Color Hit
// Color Jump
// ColorFill
// Columns
// Concentration
// Crossy Road
// Crush the Castle
// Cube Jump
// CubesOut
// Dash N Blast
// Dashy Panda
// Deflection
// Diamond Digger Saga
// Don't touch the spikes
// Dots
// Down The Mountain
// Drag and Match
// Draw Game
// Drop Wizard
// DROP'd
// Dudeski
// Dungeon Raid
// Educational Game
// Elasticity
// Endless Runner
// Erase Box
// Eskiv
// Farm Heroes Saga
// Filler
// Flappy Bird
// Fling
// Flipping Legend
// Floaty Light
// Fuse Ballz
// GearTaker
// Gem Sweeper
// Globe
// Goat Rider
// Gold Miner
// Grindstone
// GuessNext
// Helicopter
// Hero Emblems
// Hero Slide
// Hexagonal Tiles
// HookPod
// Hop Hop Hop Underwater
// Horizontal Endless Runner
// Hundreds
// Hungry Hero
// Hurry it's Christmas
// InkTd
// Iromeku
// Jet Set Willy
// Jigsaw Game
// Knife Hit
// Knightfall
// Legends of Runeterra
// Lep's World
// Line Rider
// Lumines
// Magick
// MagOrMin
// Mass Attack
// Math Game
// Maze
// Meeblings
// Memdot
// Metro Siberia Underground
// Mike Dangers
// Mikey Hooks
// Nano War
// Nodes
// o:anquan
// One Button Game
// One Tap RPG
// Ononmin
// Pacco
// Perfect Square!
// Perfectionism
// Phyballs
// Pixel Purge
// PixelField
// Planet Revenge
// Plants Vs Zombies
// Platform
// Platform game
// Plus+Plus
// Pocket Snap
// Poker
// Pool
// Pop the Lock
// Pop to Save
// Poux
// Pudi
// Pumpkin Story
// Puppet Bird
// Pyramids of Ra
// qomp
// Quick Switch
// Racing
// Radical
// Rebuild Chile
// Renju
// Rise Above
// Risky Road
// Roguelike
// Roly Poly
// Run Around
// Rush Hour
// SameGame
// SamePhysics
// Save the Totem
// Security
// Serious Scramblers
// Shrink it
// Sling
// Slingy
// Snowflakes
// Sokoban
// Space Checkers
// Space is Key
// Spellfall
// Spinny Gun
// Splitter
// Spring Ninja
// Sproing
// Stabilize!
// Stack
// Stairs
// Stick Hero
// String Avoider
// Stringy
// Sudoku
// Super Mario Bros
// Surfingers
// Survival Horror
// Talesworth Adventure
// Tetris
// The Impossible Line
// The Moops - Combos of Joy
// The Next Arrow
// Threes
// Tic Tac Toe
// Timberman
// Tiny Wings
// Tipsy Tower
// Toony
// Totem Destroyer
// Tower Defense
// Trick Shot
// Tunnelball
// Turn
// Turnellio
// TwinSpin
// vvvvvv
// Warp Shift
// Way of an Idea
// Whack a Creep
// Wheel of Fortune
// Where's my Water
// Wish Upon a Star
// Word Game
// Wordle
// Worms
// Yanga
// Yeah Bunny
// Zhed
// zNumbers