Hard puzzles are fine. Unskippable hard puzzles are less fine.
You might want to make it much clearer what the aim is, and if there are multiple solutions. Bullet points might be useful? I don't know what I'm supposed to be lining up - vertical colours? Horizontal colours? Vertical shapes? Horizontal shapes? Vertical colours and horizontal shapes (etc etc).
Sliding block puzzles normally start with very simple levels - move one block to win. Perhaps if I'd played a couple of tutorial levels I might stick at it.
Sorry this all seems negative! I'm trying to at least be constructive.
Shapes and colors (independent of each other) can be matched horizontally and vertically. Maybe I should somehow indicate when they are "locked" and that would be enough.
Actually it's a one-off puzzle to unlock a door to another level and it does not repeat. So, there's no time for tutorials.
I guess I will make this one optional, and maybe just create a simpler puzzle (say, colors only) for the unskippable door lock.
You might want to make it much clearer what the aim is, and if there are multiple solutions. Bullet points might be useful? I don't know what I'm supposed to be lining up - vertical colours? Horizontal colours? Vertical shapes? Horizontal shapes? Vertical colours and horizontal shapes (etc etc).
Sliding block puzzles normally start with very simple levels - move one block to win. Perhaps if I'd played a couple of tutorial levels I might stick at it.
Sorry this all seems negative! I'm trying to at least be constructive.