# How to change object size upon bouncing in p5.play
**URL:** https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540
**Category:** Libraries
**Created:** [December 21, 2019, 12:55am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540 "2019-12-21T00:55:11Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@blkpanther](https://discourse.processing.org/u/blkpanther)
#### Post date: [December 21, 2019, 12:55am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540/1 "2019-12-21T00:55:12Z")
I don’t know how to change the length of an object upon bouncing interaction in p5.play. In the code below, I wish to make the bar shorter from the top upon every hit, but don’t know what keyword to search for in the reference doc. Any suggestions?
```auto
var bals = [];
function setup() {
createCanvas(400, 400);
ball = createSprite(200, 10, 12, 12);
bar = createSprite(200, 300, 2, 100);
bar.immovable = true;
}
function draw() {
background(255);
if (frameCount % 120 == 0) {
bal = createSprite(200, 10, 12, 12);
bals.push(bal);
}
for (i = 0; i < bals.length; i++) {
bals[i].setSpeed(2, 90);
bals[i].bounce(bar, shortenBar);
}
drawSprites();
}
function shortenBar(ball, bar) {
ball.remove();
//make bar 10pixel shorter at the top upon each hit
}
```
Besides, how to make a sprite circular in shape as the default is square?
Thanks for your help!
---
### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [December 21, 2019, 3:07am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540/2 "2019-12-21T03:07:59Z")
hi, is the idea about
HAMMER and NAIL ?
-a- that is a p5.js question, so better as posting code is
to link to your
[https://editor.p5js.org](https://editor.p5js.org)
project
-b- you use createSprite?
so it could have helped to say that
you use a library
[http://molleindustria.github.io/p5.play/](http://molleindustria.github.io/p5.play/) ;
-c- you make a NAIL and call it immovable,
but actually you want it to move
++ disable immovable
++ make it heavy
++ give it friction
-d- also why the NAIL should be round?
but possible with using
```auto
ball.draw = function() { ellipse(0,0,20,20) }
```
example:
[https://editor.p5js.org/kll/sketches/\_1NnYvVhB](https://editor.p5js.org/kll/sketches/_1NnYvVhB)
what adds also random HAMMER
color and x position
for fun
---
### Author:  [@blkpanther](https://discourse.processing.org/u/blkpanther)
#### Post date: [December 21, 2019, 3:30am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540/3 "2019-12-21T03:30:47Z")
Thank you for your reply. Actually the bar isn’t a nail, and I need it to shorten upon each hit instead of moving down. Is there a way to do that?
---
### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [December 21, 2019, 3:37am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540/4 "2019-12-21T03:37:13Z")
sorry, as i state in the example code i not know that library.
you could worst case use a
`sprite.remove();`
and make a new one on a lower position…
but i know that is actually not the point, it is how to use the collision event?
[https://molleindustria.github.io/p5.play/docs/classes/Sprite.html#method-bounce](https://molleindustria.github.io/p5.play/docs/classes/Sprite.html#method-bounce)
!make your own bounce code
`sprite.height -=1;`
could also work inthere
---
### Author:  [@blkpanther](https://discourse.processing.org/u/blkpanther)
#### Post date: [December 21, 2019, 4:34am UTC](https://discourse.processing.org/t/how-to-change-object-size-upon-bouncing-in-p5-play/16540/5 "2019-12-21T04:34:17Z")
Thanks! You pointed me to the right direction. Adjusting height and y position will solve the problem.