// size of the circle
int s = 10;

void setup() {
  size(400, 400);
  smooth();
}

void draw() {
  if (keyPressed) {
    // large
    if (key == 'l') {
      s = 100;
    }
    // medium
    if (key == 'm') {
      s = 50;
    }
    // small
    if (key == 's') {
      s = 20;
    }
  }
  
  fill(255, random(100, 255), random(100, 255));  
  ellipse(random(width), random(height), s, s);
}