A really nice game! My small nitpick is that I would want to be able to place abilities before the loop starts, but it's no big deal. Apart from that, maybe you could think about making the game better encourage different strategies. Currently, it's mostly about spreading the health ability across the tiles. I would consider making enemies stick to a certain area and allow players to see them while building the path. Then, they could choose either to engage with tougher enemies or not, with the former obviously netting better rewards. With enemies tracking the player as-is, it can get a bit janky with slower enemy units that are artificially sped up during the end of the loop.
Still, I really like this. It's a great foundation for something. :) Well done!