Who can spot the difference?

Question

My family and I have just moved house! Lucky us!

So what did my family do? We held a housewarming party, and rung everyone in the neighbourhood up to invite them.

So, anyway, people were coming in while we were in the middle of conversations, so we decided to leave the front door open.

Then along came an old man (who I later found out lived next door), tapping his walking stick everywhere and causing a big fuss. That wasn't the worst of it! He brought in a lot of sticks from outside into our living room, and knocked everything around that we'd unpacked. After a while, a little kid said, "Grandpa, I think it's time to go home."

But it was already too late – have a look at the trail of destruction he'd unleashed! Look at the marbles that had gone everywhere! The blocks, the balls, my Puzzling notes! An abacus, a calculator, the matchstick puzzle I was working on! You get the point! Previously, everything was in a neat pile! I'm surprised he didn't knock the whole bookshelf down!

Now some stuff's gone missing, though surprisingly some things that we thought were missing have been found. Still, I've got a good mind to give this grandfather a stern talking to. But before I do, I'd like to ask for a second opinion, in case there's something I've missed. Is there a reason for me to keep my temper?

Oh, and here's a picture of the damage, so you can make an unbiased decision:

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(Hereon is not part of the puzzle, just some random notes)

Thanks to TheGreatEscaper for helping to test-solve part of the puzzle!

For those who still appreciate the art of freehand circles, this puzzle (apart from the post text) was made completely in MS Paint.

If this appears in the LQP queue for a subjective title, please don't change it! It's part of the puzzle...

There's also a smidgen of reverse-puzzling involved.

Unconventional Tag Fusion alert!

^{This story is based on a fictional event and taken from there...}

Part of an upcoming metapuzzle.

Answer 1

If you click the image to see the damage, you notice:

it leads to a different image! Taking all the differences between these two images gives:

which looks suspiciously like a Slitherlink puzzle.

However,

if you try to solve it, you run into a problem.

Er, several problems. There are a ton of ambiguities there!

So let's take a closer look at those:

They're all aligned on a grid, which suggests that we only look at the locations of the ambiguities.
The reference to the man not being able to see well (needing a walking stick), and the first letters of the titles of the books all suggest Braille.

Marking all those locations gives:

which spells HE IS BLIND in Braille.

Answer 2

Wrap-up: The Making Of Who Can Spot the Difference?

This is not a solution to the puzzle, but provides notes from its poser. This type of answer has been approved by the community.

Caution: This post may contain spoilers.

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Inspiration

The first thing that came was the title. This was back when a lot of puzzles with click-bait titles were being posted.

The idea sat in the back of my mind for a while. I cycled between text and images, but couldn't find a way to encode two messages without it being overly obvious. Eventually, I thought of taking inspiration from what heaps of puzzles before me had done, and taking advantage of the fact that you can click an image and get a different image. Once you had the two images, you could easily overlay them.

You can see this in the puzzle:

The square blocks and cylindrical/conical blocks, when interpreted as dots and dashes, spell -.-. .-.. .. -.-. -.- or CLICK.

Also, when you look at the cubes that are in pairs, in order by number, you get XORPICS:

Creative steps

What could I hide in the images? That brought me back to one of my favourite genres of puzzle: grid-deduction (even if I'm not very good at them).

This is where the reverse-puzzling came in:

There's a mini-slitherlink there, with numbers encoded as dots. If you didn't get what [g.d] means, it's hinted at down here:

How to hide a message in grid? Remembering back to Coloring a 4 by 4 grid, why not make things ambiguous? Then the ambiguities could hide a message, in braille.

Ambiguous and ambiguity each had a hint, referencing the question and comment that were just linked to:

Also, as Deusovi mentioned, the first letters of the book titles spell BRAILLE, hinted at by:

There was also a final clue to what to do with the ambiguities:

The slitherlink indeed does have $2^{23}$ solutions, and using the set notation over all the solutions you get the braille, in squares:

$$\bigcup^{2^{23}}_{i}s_i\setminus\bigcap^{2^{23}}_{i}s_i$$

Logistical steps

First, I made the slitherlink, and sent it off for testsolving to TheGreatEscaper.

I then constructed the image around the places where the differences had to be. There was a lot of freedom in this, I just had to make sure there was the Braille clue in there. I added the other clues because I ran out of things I could think of to include.

The final image looked like this, where red is in the main puzzle image and out of the hidden image, and vice versa for purple:

^{For the previous two images click on them and remove the m just before the .png to get a full-sized image.}

Resources

MS Paint was the main resource I used, although I also used OneNote to design the slitherlink because it has an easier-to-use interface.

Takeaway

Well, this puzzle was not too complicated to solve according to Deusovi ♦, who also said he liked it, which is a good sign! :D

I need to find some way of making my puzzles just right, most are either a bit easy or too hard because of a leap of intuition. I haven't learnt how to get that right, but I'm looking to improve...

Hope you liked the puzzle!