It's a great puzzle game!
The visuals are a bit simplistic (I was hoping to see more crayon drawings, that would be cool!), but they work well for the purpose of being easily readable.
This calm music perfectly fits the tactical gameplay.
I had a minor issue with a tiny game window on a 4k display, but that could be easily solved on my side by switching the resolution to 800x600.
I can see that controls are already mentioned in the comments, here are my opinion on how they could be improved (I am pretty sure you know all of that, but just in case):
- unify the menu option selection between choosing an action and choosing a skill (e.g. use arrows+enter in both menus)
- use the same buttons for the same actions in different situations (e.g. "enter" to confirm and "backspace"/"esc" to cancel the command or go back in the menu)
It was surprising to see my tactics of running away and placing crystals worked so well on the last level ¦3