Cool idea, but the units are way too small even in fullscreen. I also didn't like how you can only control one area at a time, meaning you can't really make use of the enemies' weaknesses if there are units in a further biome. The damage is way too low to be able to switch between biomes and you kind of have to constantly attack enemies in the one closest to the treasure.
Since this is more or less a tower defense game, I would love to be able to say, place clouds that shoot lightning bolts on a cooldown. Plants that spit poison, icicles/avalanches that damage enemies. Bonus points if you had to influence the environment to change so that a specific type of tower can be built (or grows naturally).
All in all, a cool concept that falls a bit short in execution. Still had fun though, and it's a lot for a two day long jam, so good job!