keymap.c

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
  if (timer_elapsed(tt_timer) > 500) {
    press_count = 0;
  }
  switch (keycode) {
    case TT_LL: {
      if (record->event.pressed) {
        if (layer_state_is(_LOWER)) {
          layer_off(_LOWER);
          press_count = 0;
          tt_timer = 0;
        } else {
          press_count += 1;
          layer_on(_LOWER);
          tt_timer = timer_read();
        }
      } else {
        if (press_count < 3) {
          layer_off(_LOWER);
        }
      }
      break;
    }
  }
  return true;
}