Wow! Really pleasantly surprised by this. Really impressive how well everything works for being a jam game. Definitely has some scaling and balancing problems - but for this kind of game I think it's better to make the player become a god too easily than make it brutally hard (for average player enjoyment purposes). My recommendations for if you keep updating this: look at how Mindustry does combat balancing. Air units vs ground units, slower and higher damaging turrets to deal with tankier enemies, turrets that are really good but miss air units, etc. All good reference material to think about.