#include <Keypad.h>

#define ROW_NUM 4
#define COL_NUM 4

byte score = 0;
byte chances;

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

byte rowPins[ROW_NUM] = { 19, 18, 5, 17 };
byte colPins[COL_NUM] = { 16, 4, 2, 15 };

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROW_NUM, COL_NUM);

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

void loop() {
  chances = 5;
  byte row = random(0, 4);
  byte col = random(0, 4);
  char rand_elem = keys[row][col];
  Serial.println("Guess the button! You have 5 chances.");

  while (true) {
    char k = keypad.getKey();
    if (k) {
      if (k == rand_elem) {
        Serial.println("Correct! Your score is " + String(++score) + "\n");
        break;
      }
      else {
        if (--chances > 0) {
          Serial.println("Whoops! You have " + String(chances) + " more chances.");
        }
        else {
          Serial.println("Oh no, you lose! Your score is " + String(score));
          while(true) delay(10000);
        }
      }
    }

    delay(100);
  }

  delay(1000);
}