FablabSU

void setup() {
  orientation(LANDSCAPE);
  size(displayWidth, displayHeight);
}
 
void draw() {
  background(0);
  fill(255);
  if (mouseX >width/2) {
    rect(0, 0, width/2, height);
  }
  else {
    rect(width/2, 0, width/2, height);
  }
}