Oooo, nifty lil' game you got. Really like the concept of an RTS-like with an upgrade system after each level. Would be really cool to see how you could develop this if you continue. More enemies, random abilities for units, different levels with obstacles? Game kind of reminds of a mish-mash between XCOM and of course Helldivers 2. Do in fact like those games with murdering swarms of enemies, so the RTS decision was a good touch!
Eitherway, cool stuff!
- S. "Essay"