# Help needed to create Gravity effect on character for sink or swim effect

**URL:** https://forum.kirupa.com/t/help-needed-to-create-gravity-effect-on-character-for-sink-or-swim-effect/325898
**Category:** programming
**Created:** [November 10, 2011, 4:57pm UTC](https://forum.kirupa.com/t/help-needed-to-create-gravity-effect-on-character-for-sink-or-swim-effect/325898 "2011-11-10T16:57:16Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![pollo\_s](https://avatars.discourse-cdn.com/v4/letter/p/bbe5ce/32.png) [@pollo\_s](https://forum.kirupa.com/u/pollo_s)
#### Post date: [November 10, 2011, 4:57pm UTC](https://forum.kirupa.com/t/help-needed-to-create-gravity-effect-on-character-for-sink-or-swim-effect/325898/1 "2011-11-10T16:57:16Z")

</div>

Hi there, Im making a simple game where the up key needs to be tapped to keep the character (bird) in the air. A bit like a helicopter effect. The code used must be AS3, and at the moment I have no movie clips on the stage everything is called via classes. Currently I have

There is a class that handles the bird  
package  
{  
import flash.display.MovieClip;  
public class Bird extends MovieClip  
{  
public function Bird()  
{

}

public function moveABit( xDistance:Number, yDistance:Number ):void  
{  
var baseSpeed:Number = 3;  
x += ( xDistance \* baseSpeed );  
y += ( yDistance \* baseSpeed );  
}

\*and a game driver class  
\*  
package  
{  
import flash.display.MovieClip;  
import flash.utils.Timer;  
import flash.events.TimerEvent;  
import flash.events.KeyboardEvent;  
import flash.ui.Keyboard;  
import flash.events.Event;  
public class GameDriver extends MovieClip  
{  
public var allheads:Array;  
public var bird:Bird;  
public var gameTimer:Timer;  
public var downKeyPress:Boolean;  
public var upKeyPress:Boolean;  
public var leftKeyPress:Boolean;  
public var rightKeyPress:Boolean;

public function GameDriver() // constructor  
{  
downKeyPress = false;  
upKeyPress = false;  
leftKeyPress = false;  
rightKeyPress = false;

allheads = new Array();  
var newHead = new Head( 100, 200 ); // numbers in brackets represent starting position  
allheads.push( newHead );  
addChild( newHead );;

bird = new Bird();  
addChild( bird );

gameTimer = new Timer( 25 );  
gameTimer.addEventListener( TimerEvent.TIMER, onTickofTimer);  
gameTimer.start();

addEventListener( Event.ADDED\_TO\_STAGE, onAddToStage );  
} // end constructor

public function onAddToStage( event:Event ):void  
{  
stage.addEventListener( KeyboardEvent.KEY\_DOWN, onKeyPress );  
stage.addEventListener( KeyboardEvent.KEY\_UP, onKeyRelease );  
} // end onAddtoStage  
public function onKeyPress( keyboardEvent:KeyboardEvent ):void  
{  
if ( keyboardEvent.keyCode == Keyboard.DOWN )  
{  
downKeyPress = true;  
}  
else if ( keyboardEvent.keyCode == Keyboard.UP )  
{  
upKeyPress= true;  
}  
else if ( keyboardEvent.keyCode == Keyboard.LEFT )  
{  
leftKeyPress = true;  
}  
else if ( keyboardEvent.keyCode == Keyboard.RIGHT )  
{  
rightKeyPress = true;  
}  
}// end on keypress  
public function onKeyRelease( keyboardEvent:KeyboardEvent ):void  
{  
if ( keyboardEvent.keyCode == Keyboard.DOWN )  
{  
downKeyPress = false;  
}  
else if ( keyboardEvent.keyCode == Keyboard.UP )  
{  
upKeyPress= false;  
}  
else if ( keyboardEvent.keyCode == Keyboard.LEFT )  
{  
leftKeyPress = false;  
}  
else if ( keyboardEvent.keyCode == Keyboard.RIGHT )  
{  
rightKeyPress = false;  
}  
}// end on keyrelease

public function onTickofTimer( timerEvent:TimerEvent ):void  
{  
if ( Math.random() \< 0.3 ) // speed at which heads appear  
{  
var headDistributionX:Number = Math.random() \* 400;  
var newHead:Head = new Head( headDistributionX, 200 );// start position of head  
allheads.push( newHead );  
addChild( newHead );  
}

/////////controls  
if ( downKeyPress )  
{  
bird.moveABit( 0, 1 );  
}  
else if ( upKeyPress )  
{  
bird.moveABit( 0, -1 );  
}  
else if ( leftKeyPress )  
{  
bird.moveABit( -1, 0 );  
}  
else if ( rightKeyPress )  
{  
bird.moveABit( 1, 0 );  
} ///////////// end controls  
///// WHAT HAPPENS WHEN BIRD HITS HEAD  
for each ( var head:Head in allheads )  
{  
head.moveHead();  
if ( bird.hitTestObject( head ) )  
{  
gameTimer.stop();

var gameOver:EndGame = new EndGame();  
gameOver.x = 0;  
gameOver.y = 0;  
addChild( gameOver );  
}  
}  
} // end for each  
}// end tick of timer  
}

Aologies for the long post, but my hair has been turning grey over this. The only tutorial i have found is for a helicopter and is great but uses AS2 to create the gravity like effect, unfortunately I cant use AS2 and i am in general i complete beginner so any help would be very much appreciated!!