# Very Basic TileBased Collision Detection

**URL:** <https://forum.kirupa.com/t/very-basic-tilebased-collision-detection/313612>\
**Category:** flash\
**Created:** [September 4, 2010, 10:11am UTC](https://forum.kirupa.com/t/very-basic-tilebased-collision-detection/313612 "2010-09-04T10:11:31Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![moselekm](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@moselekm](https://forum.kirupa.com/u/moselekm)\
**Post date:** [September 4, 2010, 10:11am UTC](https://forum.kirupa.com/t/very-basic-tilebased-collision-detection/313612/1 "2010-09-04T10:11:31Z")

</div>

So I’ve never dealt with collision detection since I mostly have just made simple web-designs, apps, and things that just don’t make use of physics or anything like that.

But today I decided to fiddle with it a little and was pretty excited when I started out just using a square to move around with keys and so I made some walls to figure out some collision stuff.

And basically, I can’t move out of the wall once I collide. I know I could make it so when I collide the sprite backs off a few pixels, but it causes that jittery effect. So I was wondering is it possible to check for a collision before the block is animated?

I’ve searched online for a while, everything seems to be scripted for as2 and just isn’t what I’m looking for.

Below is my sloppy testCode on the stage just to get my bearings before I implement anything in classes. The two sprites in use are sloppily instanced named: person, wall.

```php
import flash.events.Event;
import flash.events.KeyboardEvent;

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyedDown);
stage.addEventListener(KeyboardEvent.KEY_UP, keyedUp);
this.addEventListener(Event.ENTER_FRAME, frameHandler);

var keyIsDown:Boolean = false;

var keyUP:Boolean = false;
var keyDOWN:Boolean = false;
var keyLEFT:Boolean = false;
var keyRIGHT:Boolean = false;

var speed:Number = 5;

function frameHandler(e:Event):void
{
    if (keyIsDown)
    {
        if (keyLEFT)
        {
            if (! this.person.hitTestObject(this.wall))
            {
                this.person.x -= speed;
            }
        }
        if (keyRIGHT)
        {
            if (! this.person.hitTestObject(this.wall))
            {
                this.person.x += speed;
            }
        }
    }
}

function keyedDown(e:KeyboardEvent):void
{
    keyIsDown = true;
    switch (e.keyCode)
    {
        case 65 :
            keyLEFT = true;
            break;
        case 68 :
            keyRIGHT = true;
            break;
        default :
            break;
    }
}

function keyedUp(e:KeyboardEvent):void
{
    keyIsDown = false;
    
    keyUP = false;
    keyDOWN = false;
    keyLEFT = false;
    keyRIGHT = false;
}

```

Also to add onto my question.

What if I wish to check collisions on ‘barrier’ boolean propertied tiles? Like if I made impassable terrain, how does one check that for collisions on a wide scale?