Solution to the empty square puzzle

In Alcazar, easy puzzles can be solved either with logic, or intuition. But as puzzles get larger and harder, intuition alone will not be enough. That's why it's good to start sharpening your logic skills with small puzzles, like the one I proposed in my last post.

There are several ways to solve this puzzle step by step. Here is one method I like, because it contains several different tricks and techniques.

First, there is only one way to enter and exit each of the corners, so it's a good idea to start by filling these 4 squares.

Then, notice that there are only 2 exits in this problem. We need to use them both, otherwise we won't be able to enter and exit the room.

At this stage, the two squares near the exits are complete, which leaves only one possibility for the 2 squares on top of them.

Now, we created a "C" shape in the top-left corner. To avoid closing the loop, we must complete the line on top of the puzzle.

If we did the same on the bottom side, this would create a path that enters and exits the puzzle without visiting the whole room. The only way to avoid that is to move up.

Finally, to complete the puzzle, we have to link the top-half with the bottom-half, and there is only one way to achieve that.

It's done! And in every step, there was no other alternative. This proves that the problem had a unique solution.