The Witness marsh puzzle: Valid solution not accepted? [SPOILERS]

Question

I breezed through most of the Marsh area, then got stuck for hours on the puzzle below before giving up and looking up the answer online. I was frustrated to find that the "correct" answer appears to operate on logic that I thought I had already tested and rejected.

Here's my current understanding of how the blocks work in the puzzle below:

• You must place all yellow blocks in some configuration on the grid, then trace an outline around them. Yellow blocks can't overlap.
• For the purposes of this specific puzzle, all blocks "mesh" into 1 large outline, and none can be rotated.
• All yellow and blue blocks must be included in the overall outline shape.
• For each blue empty individual square included in the total shape, you must remove 1 square from a yellow shape before placing it.

Here's the accepted solution, which is pretty straightforward: the bottom-left yellow block sits in the bottom-left corner, with all but the corner square removed; the bottom-right block sits in the bottom-right corner, with no squares removed; and the top-right yellow block sits all the way in the top right corner, with the bottom square removed.

And here's another solution I had already tried, that was rejected, leading me to make incorrect conclusions about how the blue empty blocks worked. As far as I can tell, this is also pretty straightforward: the bottom-left block sits in the bottom-left corner, with all but the corner square removed; the bottom-right block sits in the bottom-right corner, with no squares removed; and the top-right yellow block stands in the middle, with its top-left square removed.

So my question is: Why is solution 1 accepted but solution 2 rejected? Am I misunderstanding the logic of this puzzle? (I don't mind spoilers at this point, I'm just desperate to sort out whether this is a bug or a genuine confusion on my part!)

Answer 1

That's because the blue squares are "stuck together". In this state, you need to remove 4 squares in a square shape, not just any 4 squares.

You're wrong in your assumption of why the 1st answer works. What really happens is this :

• Bottom left block at the bottom right (red dots).
• Bottom right block at the bottom left (green dots).
• Top right block at the top right corner (purple dots).
• Square removed (blue dots).

By doing that, you merge the 2 bottom blocks (imagine the middle part with 2 blocks on top of one another). That allows you to remove the 4 blocks in a square pattern (blue dots).