I'm working on an escape room for my university with an Arduino Mega. The last part consists of a 7segment display representing a time countdown, and the participants have to introduce the correct number in a matrix keyboard before it reaches zero.

My problem comes when for representing the seconds in the countdown, I have to use a delay, and this stops the matrix keyboard from getting the numbers.

The code I have so far:

char keys[4][4] = 
{
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};

byte rowPins[4] = { 5, 4, 3, 2 };
byte colPins[4] = { 9, 8, 7, 6 };

int pinA = 26; //2
int pinB = 34; //3
int pinC = 31; //4
int pinD = 27; //5
int pinE = 25; //6
int pinF = 28; //7
int pinG = 33; //8
int D1 = 24; //9
int D2 = 30; //10
int D3 = 32; //11
int D4 = 35; //12

Keypad mykeypad = Keypad( makeKeymap(keys), colPins, rowPins, 4, 4);

void setup()
{
Serial.begin(9600);


pinMode(pinA, OUTPUT);     
pinMode(pinB, OUTPUT);     
pinMode(pinC, OUTPUT);     
pinMode(pinD, OUTPUT);     
pinMode(pinE, OUTPUT);     
pinMode(pinF, OUTPUT);     
pinMode(pinG, OUTPUT);   
pinMode(D1, OUTPUT);  //Turns the first digit on.
pinMode(D2, OUTPUT);  //Turns the second digit on.
pinMode(D3, OUTPUT);  //Turns the third digit on.
pinMode(D4, OUTPUT);  //Turns the forth digit on.
}

//
void showTime(){
  
  digitalWrite(D1, LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D3, LOW);
  digitalWrite(D4, LOW); 

 //3
  digitalWrite(pinA, HIGH);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, HIGH);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, HIGH);     
  delay(1000);   

//2
  digitalWrite(pinA, HIGH);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, HIGH);     
  delay(1000); 

  //1
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, HIGH);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);   
  delay(1000); 
  
  //0
  digitalWrite(pinA, HIGH);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, HIGH);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, HIGH);   
  digitalWrite(pinG, LOW);   
  delay(1000);               
   
}

//Receives the chars from the matrix keyboard.
void getCode(){
   char key = mykeypad.getKey();
  if(key){
     Serial.print(key);
  }
}

void loop() 
{

  showTime();

}

Any idea on how can I archieve this combination? Have been trying to find something similiar to a Thread, but Arduino doesn't support it.

Thanks in advance.