The skills in this game have a cooldown based on how many pieces of the puzzle you solve.
There are skills in the game that solve puzzle pieces for you. However, you can "solve" a solved puzzle piece (that was solved by a skill) again by unsolving the puzzle piece and solving it again.

So the strategy is: Use a skill to solve puzzle pieces, then unsolve the piece (turning it left/right) then solve it again (by turning the piece you unsolved back to its original position). Doing this on a few different pieces will reduce the cooldown of all your skills. Rinse and repeat.

I used this set of skills, but there are probably other ways to do it.

Flash Bomb:
Solves in a highlighted area, very easy to see and re-solve all the affected pieces, which should be enough to lower its own cooldown to be used again.


Earthquake:
Scrambles up a few pieces so you can reuse Flash Bomb in the same area. You can Earthquake, then Flash Bomb the same area over and over again while Love Hot Dog and Chocolate Airstrike finish the rest of the puzzle. It's nice as it also rotates the entire board sometimes.

Love Hot Dog:
Solves pieces when you solve pieces.




Chocolate Airstrike:
Same as Love Hot Dog, but on a longer cooldown and much bigger.





Shimmering flare + Solve Random:
Quality of life to notice the few remaining pieces, then to automatically solve them. Also allows you to keep Flash Bomb off cooldown for the next puzzle.

Mirroring:
I hate the mirror pieces

If anyone who knows me finds this, I got this as a joke and I swear I didn't enjoy the 4 hours I spent unlocking all the achievements and items.
I realise I just spent about 30 minutes writing a guide for a hentai game. I hope it can help at least someone out there to not get frustrated while trying to unlock everything.
The art is great tho