Black And White

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

void loop() {
  if (Serial.available() > 0) {
    char ch = Serial.read();
    if(ch == '1') digitalWrite(8, HIGH);
    else digitalWrite(8, LOW);
  }
}

import processing.serial.*;

Serial serial;
int pMouseX = 0;

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

void draw() {
  fill(0);
  rect(0, 0, 160, 200);
  fill(255);
  rect(160, 0, 160, 200);
  
  if(pMouseX < 160 && mouseX >= 160) {
    serial.write('1');
  } else if(pMouseX >= 160 && mouseX < 160) {
    serial.write('0');
  }
  pMouseX = mouseX;
}