// uses a for loop to fill the screen with grey circles

void setup() {
  size(800,800);
  background(51); // grey
  int numCircles = 20;  // change this for more/less circles!
  float circleStep = width/numCircles; // figure out the space between the circles
  float colorStep = 255/numCircles; // figure out the amount of grey to add to the next circle
  for ( int i = 0 ; i < numCircles ; i++ ) {  // for each circle we will draw
    fill(i * colorStep);  // make it one step more grey than the last one
    ellipse(width/2,height/2,width-i*circleStep,width-i*circleStep); // and position it one step away from the last one
  }
}
void draw() {
}