private void turn(TURN_DIR dir) {
		if (dir == TURN_DIR.LEFT) {
			switch (this.direction) {
			case NORTH: this.direction = DIRECTION.WEST; break;
			case WEST: this.direction = DIRECTION.SOUTH; break;
			case SOUTH: this.direction = DIRECTION.EAST; break;
			case EAST: this.direction = DIRECTION.NORTH; break;
			}
		} else {
			switch (this.direction) {
			case NORTH: this.direction = DIRECTION.EAST; break;
			case WEST: this.direction = DIRECTION.NORTH; break;
			case SOUTH: this.direction = DIRECTION.WEST; break;
			case EAST: this.direction = DIRECTION.SOUTH; break;
			}
		}
	}