Cool game, one tweak I'd reccomend is making hero hitboxes bigger on the back side.
In PVZ, you could stall with plants by replanting instantly after one is destroyed either to get a few extra hits in with a peashooter(if the zombie was in front of the plant enough) but mostly to just buy time with HP like via a wallnut.
In this game, you can't do that as easily bc the H-scene blocks immediate replanting, but it is also frustrating to put a shield guy right on top of an enemy and watch as the enemy keeps walking right through it.