# A few questions about collisions (Phaser 3.24.1 + PhaserMatterCollisionPlugin) \[RESOLVED\]

**URL:** <https://phaser.discourse.group/t/a-few-questions-about-collisions-phaser-3-24-1-phasermattercollisionplugin-resolved/7653>\
**Category:** Phaser 3\
**Created:** [October 11, 2020, 7:31pm UTC](https://phaser.discourse.group/t/a-few-questions-about-collisions-phaser-3-24-1-phasermattercollisionplugin-resolved/7653 "2020-10-11T19:31:22Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Azowarg](https://avatars.discourse-cdn.com/v4/letter/a/a9adbd/32.png) [@Azowarg](https://phaser.discourse.group/u/Azowarg)\
**Post date:** [October 11, 2020, 7:31pm UTC](https://phaser.discourse.group/t/a-few-questions-about-collisions-phaser-3-24-1-phasermattercollisionplugin-resolved/7653/1 "2020-10-11T19:31:22Z")

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Good day.

I am using Phaser 3.24.1 + PhaserMatterCollisionPlugin.  
But i met one problem: how to add listener to collision with top bound?  
I am able to set collision with this method  
this.matter.world.on(‘collisionstart’, (event, bullet, topBound) =\> {  
this.destroyBullet(bullet);  
});  
But. It is possible to set some listener to collision of top bound with every object?  
I am trying to create a simple top-down shooter and want bullets must be destroyed when reached top bound.  
Just if something touch bound, event is triggered?

And one question yet: it is possible to create collide groups for matter physics?

Thanks

---

<div class="post-metadata">

**Author:** ![Azowarg](https://avatars.discourse-cdn.com/v4/letter/a/a9adbd/32.png) [@Azowarg](https://phaser.discourse.group/u/Azowarg)\
**Post date:** [October 11, 2020, 11:36pm UTC](https://phaser.discourse.group/t/a-few-questions-about-collisions-phaser-3-24-1-phasermattercollisionplugin-resolved/7653/2 "2020-10-11T23:36:45Z")

</div>

Solution:

```
    this.topBound = this.matter.world.walls.top;   
    this.matterCollision.addOnCollideStart({
        objectA: this.topBound,
        callback: event => {
            // handler        
        }
    })
```