char n_buttons = 7;
char button_pins[] = {0, 1, 2, 3, 4, 5, 6};
char pin_state[] = {HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, HIGH};

char modKey = KEY_LEFT_CTRL;

int buttons[7][6] = {
  {'1'},
  {'2'},
  {'3'},
  {'4'},
  {'5'},
  {'6'},
  {'7'}
};
char sequence_length[] = {1, 1, 1, 1, 1, 1, 1};


void setup() {
  // put your setup code here, to run once:
  for (int i = 0; i < n_buttons; ++i) {
    pinMode(button_pins[i], INPUT_PULLUP);
  }
  Keyboard.begin()
}


void loop() {
  char state = 0;
  for (int i = 0; i < n_buttons; ++i) {
    state = digitalRead(button_pins[i]);
    if (state != pin_state[i]) {
      pin_state[i] = state;
      set_button_state(i, state);
    }
  }
  delay(10);
}


void set_button_state(int button_i, char state) {
  int *sequence = buttons[button_i];
  char len = sequence_length[button_i];

  if (sequence_length[button_i] == 1) {
    if (state == LOW) {
      Keyboard.press(modKey);
      Keyboard.press(sequence[0]);
    } else {
      Keyboard.releaseAll();
    }
  } else if(state == LOW) {
    Keyboard.press(modKey);
    for (int i = 0; i < len; ++i) {
      Keyboard.press(sequence[i]);
      Keyboard.release(sequence[i]);
      delay(12);
    }
    Keyboard.releaseAll();
  }
}