Flash Oyun Yaratmak Bölüm 1 - AS3_5

import flash.events.KeyboardEvent;
import flash.events.Event;
import flash.display.MovieClip;

var speed:Number = 0.08;
var xspeed:Number = 0;
var yspeed:Number = 0;
var friction:Number = 0.98;
var gravity:Number = 0.04;
var key_left:Boolean = false;
var key_right:Boolean = false;
var key_up:Boolean = false;
var key_down:Boolean = false;

stage.addEventListener(KeyboardEvent.KEY_DOWN,KeyDown);
stage.addEventListener(KeyboardEvent.KEY_UP,KeyUp);

addEventListener(Event.ENTER_FRAME,Main);

function Main(event:Event){
    CheckKeys();
    MoveHero();
}

function KeyDown(event:KeyboardEvent){
    if(event.keyCode == 37){
        key_left = true;
    }
    if(event.keyCode == 39){
        key_right = true;
    }
    if(event.keyCode == 38){
        key_up = true;
    }
    if(event.keyCode == 40){
        key_down = true;
    }
}

function KeyUp(event:KeyboardEvent){
    if(event.keyCode == 37){
        key_left = false;
    }
    if(event.keyCode == 39){
        key_right = false;
    }
    if(event.keyCode == 38){
        key_up = false;
    }
    if(event.keyCode == 40){
        key_down = false;
    }
}

function CheckKeys(){
    if(key_left){
        xspeed -= speed;
    }
    if(key_right){
        xspeed += speed;
    }
    if(key_up){
        yspeed -= speed;
    }
    if(key_down){
        yspeed += speed;
    }
}

function MoveHero(){
    hero.x += xspeed;
    hero.y += yspeed;
    xspeed *= friction;
    yspeed *= friction;
    yspeed += gravity;
}