boolean isRed = false; // State variable

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

void draw() {
  if (isRed) {
    background(255, 0, 0); // Red background
  } else {
    background(0, 0, 255); // Blue background
  }
}

void mousePressed() {
  isRed = !isRed; // Toggle state on mouse click
}