Circles

int pButtonState = 0;

void setup() {
  pinMode(8, INPUT);
  Serial.begin(9600);
}

void loop() {
  int buttonPressed = digitalRead(8);
  if(pButtonState == LOW && buttonPressed == HIGH) {
    Serial.print('1');
  }
  pButtonState = buttonPressed;
}

import processing.serial.*;

Serial serial;

void setup() {
  size(320, 200);
  serial = new Serial(this, Serial.list()[0], 9600);
  background(0);
}

void draw() {
  if(serial.available() > 0) {
    int ch = serial.read();
    if(ch == '1') {
      int red = (int)random(255);
      int green = (int)random(255);
      int blue = (int)random(255);
      int x = (int)random(320);
      int y = (int)random(200);
      int size = (int)random(30, 100);
      fill(red, green, blue, 180);
      ellipse(x, y, size, size);
    }
  }
}