#include <LiquidCrystal_I2C.h>

#define buttonPin 2
#define buzzerPin 3
#define LIMIT 10

bool buttonState=0;
bool lastButtonState=0;
unsigned long lastDebounceTime=0;
int debounceDelay=50;

LiquidCrystal_I2C lcd(0x27, 16, 2);
uint8_t cas = LIMIT;
unsigned long previousMillis = 0;
bool stav=false;

uint8_t n = 0;
uint8_t k = 1;

byte customChar[8] = {
	0b10101,
	0b01010,
	0b11111,
	0b11011,
	0b01110,
	0b10101,
	0b00100,
	0b10101
};

void setup() {
  pinMode(buttonPin, INPUT);
  lcd.init();
  lcd.backlight();
  lcd.createChar(0, customChar);
  zobraz();
}

void loop() {
  unsigned long currentMillis = millis();
  if(currentMillis-previousMillis>=1000 && stav){
    previousMillis=currentMillis;
    --cas;
    zobraz();
    if(cas==0){
      tone(buzzerPin,262,200);
      stav=false;
    }
  }
  //debounce example
  bool reading = digitalRead(buttonPin);
  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }
  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (reading != buttonState) {
      buttonState = reading;
      if (buttonState == HIGH && !stav) {
        cas=LIMIT;
        stav=true;
        previousMillis=millis();
        zobraz();

      }
      else if(buttonState == HIGH && stav){
        stav=false;
        tone(buzzerPin,292,200);
      }
    }
  }
  lastButtonState = reading;
}

void zobraz(){
  lcd.clear();
  lcd.setCursor(7,1);
  String text=(cas<LIMIT?' '+String(cas):String(cas));
  lcd.print(text);
  lcd.setCursor(n,0);
  n=n+k;
  k=n==0||n==15?-k:k;
  lcd.write((byte)0);
}