Once I figured it out, the mechanics are very fun!
The game initially wouldn't let me zap the first wall open (I tried +2/-2/and a bunch of other values) before I reloaded and tried again. It wasn't apparent that the orbs are checkpoints (they are sorta hard to see in general)
It was not immediately apparent that the floating numbers were indicating attacks.
The game would also benefit massively from having sound.
The aesthetic of the shader is very cool but it made some of the tiles very visually noisy and hard to read. Loved the animation on the charge bar. The charge flip tile has no indicator at all, which was rough.
I also found myself losing charge from + tiles against the first enemy. The enemy had a - charge, so I attacked him with + charge which just gave him more health. It feels strange that the instructiosn say to use the opposite charge, but you are actually supposed to use the same charge.