Sometimes the layers look werid. Example: the turtle goes under some tiles.
Overall, the game feels very polished
The first puzzle in the trololo secret area does not restart, locking you out of it if you completed it and then went back. (I did that to check the other areas)
Before finishing:

After finishing (bug, you have to click R, then no way to go back):

The secret area is okay. It's not too hard to find.
Alot of puzzles can be completed in a way that feels unintended. I remember I could finish some puzzles with carts or platforms leftover without using them. Intentional? I don't know.
This will sound vague, but alot of the puzzles can be completed with a simple question "which direction to go next?" It makes it very easy to deduce the solution of the puzzles. Since you only have four directions every time, you basically only have four controls in each puzzle. You only have four choices at max in each step of the puzzles.
I understand some puzzles let you start in wrong positions, this is a good design to prevent easy deduction of the solution.
But once you're in the correct spot, all you have to do is check which direction to go. And most of the time it's very obvious which direction is the right one, because you can eliminate all the directions that AREN'T right, leaving you with the right one.
The puzzle design should prevent this deduction.
But honestly, I couldn't finish this puzzle:

Finally, I got locked here (bug):

For the game experience, it's very enjoyable. Has a nice atmosphere, has nice music that fits the mood.
