#include <TM1637.h>   // Libreria : Grove 4-Digit Display

const int CLK = 2;
const int DIO = 3;
unsigned long tempo=0;
int counter = 100;    // countdown in secondi con pausa = 1000 
int cnt= counter;
int pausa = 1000;    // millis() countdown 1 sec. con pausa = 1000 
int fast =100;       // millis() countdown veloce 
byte stato = 0;

TM1637 tm(CLK, DIO);

void setup() {
  pinMode(9, OUTPUT);
  pinMode(10,INPUT_PULLUP);
  pinMode(11,INPUT_PULLUP);
  pinMode(12,INPUT_PULLUP);
  pinMode(13,INPUT_PULLUP);
  tm.init();
  tm.set(BRIGHT_TYPICAL);
}

void loop() {
  if (!digitalRead(13) and stato !=3)(stato=1);
  if (!digitalRead(12))(stato=2);
  if (!digitalRead(11) and stato==1)(stato=3);
  if (!digitalRead(10) or counter<0)(stato=4);

  switch (stato){

    case 1:
      pausa=1000;
      countdown();
      break;

    case 2:
      while (stato==2){
       if (!digitalRead(13))(stato=1);(counter=cnt);
       if (!digitalRead(10))(stato=4);
      }
      break;

    case 3:
      pausa=fast;
      countdown();
      break;

    case 4:
      while (stato==4){
       if (!digitalRead(13))(stato=1);(counter=cnt);
         digitalWrite(9,HIGH);
         for(int i=0;i<4;i++)(tm.display(i,15));
         digitalWrite(9,HIGH);
         delay(150);
         if (!digitalRead(13))(stato=1);(counter=cnt);
         for(int i=0;i<4;i++)(tm.display(i,13));
         digitalWrite(9,LOW);
         delay(150);
      }
      break;
  }
}

void countdown(){
  if (millis()-tempo>=pausa){
  //tm.point(POINT_ON);
  tm.display(0, (counter / 1000) % 10);
  tm.display(1, (counter / 100) % 10);
  tm.display(2, (counter / 10) % 10);
  tm.display(3, counter % 10);
  counter--;
  tempo=millis();
  }
}