Arduino code to receive x and y inputs from a joystick which is then communicated to the serial monitor. The code also checks for incoming values from the serial monitor to determine when to turn off the LEDs.

Fruit_Ninja.INO

// These constants won't change. They're used to give names to the pins used:
int xAxis = A0; // Analog input pin that the x-axis of the joystick is attached to
int yAxis = A1; // Analog input pin that the y-axis of the joystick is attached to

int sensorValue1 = 0;        // value read from the potentometer
int sensorValue2 = 0;        // calue read from the photoreceptor

int LEDpin1 = 4;
int LEDpin2 = 7;
int LEDpin3 = 8;

int incomingByte;
bool life1 = true;
bool life2 = true;
bool life3 = true;

void setup() {
  // initialize serial communications at 9600 bps:
  pinMode(LEDpin1, OUTPUT);
  pinMode(LEDpin2, OUTPUT);
  pinMode(LEDpin3, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // read the analog in value:
  sensorValue1 = analogRead(xAxis);

  // read the analog in value:
  sensorValue2 = analogRead(yAxis);

  // print the analog inputs to the Serial Monitor:
  Serial.print(sensorValue1);
  Serial.print("||");
  Serial.println(sensorValue2);

  if (Serial.available() > 0) {
    incomingByte = Serial.read();
    if (incomingByte == 'A') {
      life1 = false;
    } else if (incomingByte == 'B'){
      life2 = false;
    } else if (incomingByte == 'C') {
      life3 = false;
    } else if (incomingByte == 'D') {
      life1 = true;
      life2 = true;
      life3 = true;
    }
  }

  if (life1) {
    digitalWrite(LEDpin1, HIGH);
  } else {
    digitalWrite(LEDpin1, LOW);
  }

  if (life2) {
    digitalWrite(LEDpin2, HIGH);
  } else {
    digitalWrite(LEDpin2, LOW);
  }

  if (life3) {
    digitalWrite(LEDpin3, HIGH);
  } else {
    digitalWrite(LEDpin3, LOW);
  }

  // wait 2 milliseconds before the next loop for the analog-to-digital
  // converter to settle after the last reading:
}