#include <LiquidCrystal.h>
#include <Keypad.h>

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

const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 3; 
byte rowPins[KEYPAD_ROWS] = {5, 4, 3, 2};
byte colPins[KEYPAD_COLS] = {A3, A2, A1};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3' },
  {'4', '5', '6' },
  {'7', '8', '9' },
  {'.', '0', '=' }
};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, KEYPAD_ROWS, KEYPAD_COLS);

String current = "";

void showSplashScreen() {
  lcd.print("Hello...!!");
  lcd.setCursor(3, 1);
  String message = "Enter Number";
  for (byte i = 0; i < message.length(); i++) {
    lcd.print(message[i]);
    delay(50);
  }
  delay(2000);
}

void updateCursor() {
  if (millis() / 250 % 2 == 0) {
    lcd.cursor();
  } else {
    lcd.noCursor();
  }
}

void setup() {
  Serial.begin(115200);
  lcd.begin(16, 2);

  showSplashScreen();
  lcd.clear();
  lcd.cursor();

  lcd.setCursor(1, 0);
}

void processInput(char key) {
  if (!(key == '.' && current == "0")) {
    current += String(key);
    lcd.print(key);
  }
}

void loop() {
  updateCursor();

  char key = keypad.getKey();
  if (key != NO_KEY && isDigit(key)) {
    processInput(key);
    delay(100);
  }
}