private boolean checkMove(Move move) {
		switch (map[move.toY][move.toX]) {
		case MOUNTAIN:
		case WATER:
			return false;
		default:
			break;
		}
		if (units[move.toY][move.toX] != null) {
			return false;
		}
		if (units[move.fromY][move.fromX] == null) {
			return false;
		}
		return true;
	}