void setup() {

  Serial.begin(9600);
  while (!Serial)
    ;

  if (!APDS.begin()) {
    Serial.println("Error initializing APDS-9960 sensor.");
  }

  Serial.println("READY!");
}

void loop() {

  if (APDS.gestureAvailable()) {
    // A gesture was detected, read and print to Serial Monitor.
    int gesture = APDS.readGesture();

    switch (gesture) {
      case GESTURE_UP:
        Serial.println("Detected UP gesture");
        break;

      case GESTURE_DOWN:
        Serial.println("Detected DOWN gesture");
        break;

      case GESTURE_LEFT:
        Serial.println("Detected LEFT gesture");
        break;

      case GESTURE_RIGHT:
        Serial.println("Detected RIGHT gesture");
        break;

      default:
        // Ignore.
        break;
    }
  }  //  end if gesture available


}