Okay, now I feel really stupid. Here's my code:

int xpos, ypos, wdth, ht;
void setup(){
 size(200, 200);
 wdth = int (random(100));
 ht = wdth;
 noStroke();
 xpos = width/2;
 ypos = height/2;
 frameRate(30);
}

void draw(){
 wdth = wdth + 1; // change + to -
 ht = wdth;
 ellipse(xpos, ypos, wdth, ht);
}

Okay, so when I run this, the circle enlarges smoothly. Now change the + to a - in the first line in the draw function where there is a comment. I expected the circle to shrink but it doesn't. Why?

How do I get it to shrink in size?

George