I'm glad you enjoyed the art, that was probably where 75% of my time went.
You're the second player to note that placement would be better with a grid... I thought I was being clever with the free-placement, but clearly a grid system would be better. Definitely something I'll remember if I try another game like this one.
I think your comments on the mission preview is spot-on... the "difficultly" is more what I imagined it to be when making the level ideas than how they turned out in the end. After the jam period I may go back and update that to instead list some attributes/hints about the level's design.
Thanks so much for playing, and all your feedback!