const uint8_t ledPin = LED_BUILTIN;
const uint8_t buzzerPin = 12;
const uint8_t sliderPin = A0;
const uint8_t levelMin = 30;

void setup()
{
  Serial.begin( 115200 );
  pinMode( ledPin, OUTPUT );
  delay( 50 );
}

void loop()
{
  uint32_t now = millis();
  uint8_t level = map( analogRead( sliderPin ), 0, 1023, 0, 100 );

  static bool alarm = false;
  static bool alarmTimer = false;
  static uint32_t alarmTime = 0;

  if ( alarm == false )
  {
    if ( level < levelMin )
    {
      alarm = true;
      alarmTimer = true;
      alarmTime = now;
      tone( buzzerPin, 2000 );
      Serial.println( "level < levelMin" );
    }
  }
  else
  {
    if ( level >= levelMin )
    {
      alarm = false;
      noTone( buzzerPin );
      digitalWrite( ledPin, LOW );
      Serial.println( "level >= levelMin" );
    }
    else if ( alarmTimer == true && now - alarmTime >= 5000UL )
    {
      alarmTimer = false;
      noTone( buzzerPin );
      digitalWrite( ledPin, HIGH );
    }
  }
}