#include <Arduino.h>
#include <Keyboard.h>

#define BUTTON_A 3
#define BUTTON_B 4
#define BUTTON_C 5
#define BUTTON_D 6

void setup() {
    pinMode(BUTTON_A, INPUT_PULLUP);
    pinMode(BUTTON_B, INPUT_PULLUP);
    pinMode(BUTTON_C, INPUT_PULLUP);
    pinMode(BUTTON_D, INPUT_PULLUP);

    Keyboard.begin();
}

void loop() {
    bool buttonA = !digitalRead(BUTTON_A);
    bool buttonB = !digitalRead(BUTTON_B);
    bool buttonC = !digitalRead(BUTTON_C);
    bool buttonD = !digitalRead(BUTTON_D);

    if (buttonA || buttonB || buttonC || buttonD) {
        if (buttonA) Keyboard.write('A');
        if (buttonB) Keyboard.write('B');
        if (buttonC) Keyboard.write('C');
        if (buttonD) Keyboard.write('D');

        delay(50);
    }
}