I love chess puzzle games like this! You've got a really good balance here between challenging unit placement and that rush of clearing part of the board right before you run out of space. I also really like the unique sprites that update as you add more of the same units.
I can definitely see some room to run with this concept post-jam, adding things like unique level shapes, obstacles where you can't place units (or block line of sight), handcrafted levels with their own one-off objectives and bonus challenges, etc. Nice work on this one!