const int PINS[]={12,11,10},Button[]={2,3,4,5}; //initialise pins
int ButtonState[]={-1,-1,-1,-1};//set button state to neither high nor low
unsigned long StartTime,CurrentTime,Duration=1500;
bool BuzzerOn=false,LED_On=false,Pressed[] ={false,false,false,false};
//used to check whether button was pressed
void setup() {

  for (int i=0; i<4; i++){
    pinMode(Button[i], INPUT_PULLUP);//account for resistance in wires
  }
  for (int j=0; j<3; j++){
    pinMode(PINS[j], OUTPUT);
  }
  analogWrite(PINS[2],236);
  StartTime=millis();
}

void loop() {
  //Ensure LED 2 is always blinking
  CurrentTime=millis();
  if ((CurrentTime-StartTime) >= Duration){
    digitalWrite(PINS[1],!digitalRead(PINS[1])); //reverse the state of the second LED
    StartTime=CurrentTime;
  }

  //Button 1
  ButtonState[0]=digitalRead(Button[0]);
  if (ButtonState[0]==LOW){
    Pressed[0]=true;
  }
  else if (ButtonState[0]==HIGH && Pressed[0]==true){
    if (BuzzerOn==false){
      tone(PINS[0],1000);
      Pressed[0]=false;
      BuzzerOn=true;
    }
    else{
      noTone(PINS[0]);
      Pressed[0]=false;
      BuzzerOn=false;
    }
  }

  //Button 2
  ButtonState[1]=digitalRead(Button[1]);
  if (ButtonState[1]==LOW){
    Pressed[1]=true;
  }
  else if (ButtonState[1]==HIGH && Pressed[1]==true){
    Pressed[1]=false;
    if (Duration>=200){
      Duration=Duration-100;
    }
  }

  //Button 3
  ButtonState[2]=digitalRead(Button[2]);
  if (ButtonState[2]==LOW){
    Pressed[2]=true;
  }
  else if (ButtonState[2]==HIGH && Pressed[2]==true){
    Pressed[2]=false;
    Duration=Duration+100;
  }

  //Button 4

  ButtonState[3]=digitalRead(Button[3]);
  if (ButtonState[3]==LOW){
    Pressed[3]=true;
  }
  else if (ButtonState[3]==HIGH && Pressed[3]==true){
    if (LED_On==false){
      analogWrite(PINS[2],236);
      Pressed[3]=false;
      LED_On=true;
    }
    else{
      analogWrite(PINS[2],5);
      Pressed[3]=false;
      LED_On=false;
    }
  }
}