This is a pretty cool concept and is quite interesting, albeit a bit confusing at first.
Player Health? can go pretty far into the negatives, as there doesn't seem to be a win or loss condition at all, which is great to just mess around with the cards and movement.
Similarly, even when the entire board is blue, the opponent just starts placing units down on player owned tiles.
Player owned units are able to attack infinitely, which makes combat really easy since higher attack units cannot be damage by lower attack ones. It also makes it really easy to block off opposing units.
The unit variety and effects are well implemented, though sometimes when being hit by the Death effect of the skeleton minions, enemy units would survive with 0 health remaining.
Solid foundation, interested to see where it goes next.