Finished it for the first time :-) Playing a lot more careful really pays off. Also wishlisted! Do you appreciate bug reports? Ideally on Discord for instance?
Got one for you: When you move around Synergy gems sometimes the yellow highlighting becomes broken, I think when the affected spots are outside of the 3x3 area. When you move them on a spot where they all fit it is fixed again.
Also, when I started the Hellish level I couldn't fire. Instant panic attack as you can imagine ;-) Opening and closing the map fixed it, luckily.