int btn=3;
int buzzer=10;
int code[]={1,2,1,2};
int input[4];
int step=0;
int melody[]={262,330,392,523,659,784};

void setup(){
  pinMode(btn,INPUT_PULLUP);
  pinMode(buzzer,OUTPUT);
}

void loop(){
  if(digitalRead(btn)==LOW){
    delay(50);
    int time=0;
    while(digitalRead(btn)==LOW){
      delay(10);
      time+=10;
    }
    input[step]=(time>500)?2:1;
    tone(buzzer,800,100);
    step++;
    
    if(step>=4){
      bool ok=true;
      for(int i=0;i<4;i++) if(input[i]!=code[i]) ok=false;
      
      if(ok){
        for(int i=0;i<6;i++){
          tone(buzzer,melody[i],200);
          delay(250);
        }
      }else{
        tone(buzzer,200,1000);
      }
      step=0;
      delay(1000);
    }
  }
}