#include <LiquidCrystal.h>
#define PIZ 4

#define LED_PIN 13
#define BRIGHTNESS 255


LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

volatile int timeSec = 10;
volatile int s = timeSec;

uint64_t lastTime = 0;

void setup() {
  Serial.begin(9600);
 
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("Time: ");
  lcd.print(s);
  lcd.print(" s  ");

  pinMode(2, INPUT_PULLUP);
  pinMode(3, INPUT_PULLUP);
  pinMode(PIZ, OUTPUT);

  attachInterrupt(0, pravo, FALLING);
  attachInterrupt(1, levo, FALLING);
  lastTime = millis();
}

void loop() {
  if (s == 0) {
    tone(PIZ, 2000, 3000);
    delay(3000);
    s = timeSec;
  }
  else {
    if (millis() - lastTime > 1000) {
      lastTime = millis();
      s--;
    }
  lcd.setCursor(6, 0);
  lcd.print(s);
  lcd.print(" s  ");
  }

}

void pravo() {
  s++;
  timeSec++;
}

void levo() {
  s = s > 0 ? s - 1 : 0;
  timeSec = timeSec > 1 ? timeSec-- : 1;
}