#include <Keyboard.h>

// MAMEish bindings.
struct { int pin; int key; } pinsToKeys[] = {
  { 2,  KEY_LEFT_ARROW  },
  { 3,  KEY_UP_ARROW    },
  { 4,  KEY_RIGHT_ARROW },
  { 5,  KEY_DOWN_ARROW  },
  { 6,  KEY_LEFT_CTRL }, // Fire 1
  { 7,  KEY_LEFT_ALT  }, // Fire 2
  { 8,  32 }, // space      Fire 3
  { 9,  65 }, // a          Fire 4
  { 10, 83 }, // s          Fire 5
  { 11, 81 }, // q          Fire 6
  { A0, 1  }, // 1          start
  { A2, 27 }  // esc        pause
};

void setup() {
  for (const auto& pinToKey : pinsToKeys) {
    pinMode(pinToKey.pin, INPUT_PULLUP);
  }

  Keyboard.begin();
}

void loop() {
  for (const auto& pinToKey : pinsToKeys) {
    if (digitalRead(pinToKey.pin) == LOW) {
      Keyboard.press(pinToKey.key);
    } else {
      Keyboard.release(pinToKey.key);
    }
  }
}