The characters are cute, I especially like the dark wizards who just shoot people with guns.
I would appreciate some tooltips or UI elements telling me the stat of the units I can build and what the various timers in the UI mean. I did get some impression from gameplay that skeleton = weak tank, imp = weak dps, mage = strong dps, golem = strong tank. At the start of the game I spammed a lot of skeletons and at the end I spammed a lot of mages.
The music is grating, I turned it off. Its nice you can turn it off, but slightly annoying that opening the menu automatically pauses the sound, which makes it hard to adjust volume properly (in this case it didn't matter because I just wanted it off). The sound effects are much better than the music.
The core gameplay of overwhelming your enemy with units and snowballing more territory into more money is fun. I do think the 5x5 grids slightly overstays its welcome compared to the amount of novel gameplay. But not by too much and I did complete the game.
I restarted at the end to see how different the map would be. I noticed you can get dramatically different numbers of plain fields (the easy area that gives one gold). Given that the only time you are at risk of losing is at the start before you establish a foothold any map with few fields will be a lot more difficult.
Overall a solid game jam entry.