// Global variables
const int buttonPins[] = {0,1,2,3,4,5,6};
const int ledPin = 7;
const int buzzerPin = 9;

// Note frequencies for each button
const int noteFrequencies[] = {
  262, 294, 330, 349, 392, 440, 494};

int buttonState[] = {HIGH, HIGH, HIGH, HIGH,HIGH, HIGH,HIGH};
int prevButtonState[] = {HIGH, HIGH, HIGH, HIGH, HIGH, HIGH,HIGH};

int noteDuration = 250;
int melodyLength = 7;

void setup(){
  for(int i = 0; i < 7; i++){
    pinMode(buttonPins[i], INPUT_PULLUP);
  }
  pinMode(ledPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  for(int i = 0; i < 7;i++){
  buttonState[i] = digitalRead(buttonPins[i]);
  if(buttonState[i] == LOW && prevButtonState [i] == HIGH){
    tone(buzzerPin, noteFrequencies[i], noteDuration);
    digitalWrite(ledPin, HIGH);
  }

  if(buttonState[i] ==  HIGH && prevButtonState [i] == LOW){
    noTone(buzzerPin);
    digitalWrite(ledPin, LOW);
  }

  //store the current state
  prevButtonState[i] = buttonState[i];
  }
}