# Conditions to make a circle grow and shrink
**URL:** https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698
**Category:** Beginners
**Created:** [January 15, 2024, 9:42pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698 "2024-01-15T21:42:28Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Karrajo](https://discourse.processing.org/u/Karrajo)
#### Post date: [January 15, 2024, 9:42pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/1 "2024-01-15T21:42:28Z")
Hello,
Sorry because I know this is a very simple question but I’m stuck on this and I need help.
I’m trying to create the conditions to grow a circle up to a certain point, and when it reaches that point, make it smaller (also up to a certain point, and so on). I see is similar to other topics but I think this is a different way to make it.
“tamanyo” is the variable for the original size of the circle, and “a” is the variable I am using to grow and then shrink the circle.
This is my code:
```auto
float a=0;
float tamanyo=50;
void setup(){
size(400,400);
}
void draw(){
background(0);
noFill();
stroke(255);
circle(width/2,height/2,tamanyo);
tamanyo +=a;
if (a<=0) {
a++;
}
if (a == 20){
a--;
}
}
```
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [January 15, 2024, 9:59pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/2 "2024-01-15T21:59:42Z")
1st define global constants for max & min diameters of your **circle()**:
`static final int MIN_DIAM = 3, MAX_DIAM = 100;`
2nd declare current diameter & growth speed variables:
`float diam = MIN_DIAM, growth = .5;`
Then when updating _diam_ w/ _growth_, check if _diam_ has reached either min or max diameters; if so negate the current _growth_ speed:
`if ( (diam += growth) <= MIN_DIAM || diam >= MAX_DIAM ) growth *= -1;`
---
### Author:  [@Karrajo](https://discourse.processing.org/u/Karrajo)
#### Post date: [January 15, 2024, 10:07pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/3 "2024-01-15T22:07:46Z")
Thank you, but I don’t understand the method or it’s not working:
This would be the final code?
```auto
float a=0;
float diam=50;
static final int MIN_DIAM = 3, MAX_DIAM = 100;
void setup(){
size(400,400);
}
void draw(){
background(0);
noFill();
stroke(255);
float diam = MIN_DIAM, growth = .5;
circle(width/2,height/2,diam);
diam +=a;
if ( (diam += growth) <= MIN_DIAM || diam >= MAX_DIAM ) growth += -1;
}
```
I use 3.5.3. version of processing
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [January 15, 2024, 10:19pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/4 "2024-01-15T22:19:41Z")
Why are you re-declaring global variable _diam_ as a local variable in **draw()**?
And in the same vein, why _growth_ is a local variable in **draw()**?
Both _diam_ & _growth_ need to be global variables, so their current value is remembered while **draw()** is called back during the sketch execution.
---
### Author:  [@Karrajo](https://discourse.processing.org/u/Karrajo)
#### Post date: [January 15, 2024, 10:30pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/5 "2024-01-15T22:30:02Z")
Yeah, sorry.
So this is the solution:
```auto
float diam = MIN_DIAM, growth = .5;
static final int MIN_DIAM = 3, MAX_DIAM = 100;
void setup(){
size(400,400);
}
void draw(){
background(0);
noFill();
stroke(255);
circle(width/2,height/2,diam);
if ( (diam += growth) <= MIN_DIAM || diam >= MAX_DIAM ) growth *= -1;
}
```
Thank you very much
---
### Author:  [@theapplesguy2](https://discourse.processing.org/u/theapplesguy2)
#### Post date: [July 3, 2024, 1:45pm UTC](https://discourse.processing.org/t/conditions-to-make-a-circle-grow-and-shrink/43698/6 "2024-07-03T13:45:32Z")
you could do something like this
```auto
void setup(){
size(400,400);
float g = 0;
}
float g = 0;
void draw(){
float f = (50+(sin(g)*5));
g=g+0.1;
background(56);
ellipse(200,200,f,f);
}
```