Thanks for playing all the feedback!
Yeah I'm entirely sure about what kind of music I want, but higher tempo would probably be better at least.
Concerning enemy AI, I have been experimenting a bit with smarter AI and with some local collision avoidance but I haven't seen that much benefit to it in the long run. The reason for that is the amount of enemies rise massively the further you get but so does the power of your guns; the enemies will be packed so tightly and die quickly that the behavior of an individual is barely apparent. Giving them more different behaviors though, absolutely. And the reason why you thought some of the purple ones path-finding seems to break is because units can get into different formations that changes how they act. In that instance they're protecting the "scepter" enemies, stands still and shoots, so you have to get through them to kill the shooters. I realize though that it might seem jarring if the same enemies suddenly act different, so maybe it'd be better to have them always act the same and make new ones instead?
The reason for returning after leveling up is that if you have enough runes to afford it you can level up multiple times. Might be changed in the future though. And I know its ugly as sin.
Map symbols not being obvious is a bit by design, although I made the sprites really quickly so I'll change most of them, so you'll have to go to them first to discover what they do. Right now there are 5 different ones: blue cave, red desert, rest point, shop, and boss. A lot more stuff is planned though.
About the spawner enemies; good suggestions, I'm not entirely sure how I want to handle them but I'll probably try yours. But I think they get more interesting in the later levels when there's a lot more enemies, might just remove them from the first levels actually. Also enemies have armor and that one in particular has a high amount, all guns and effects have different amounts of armor piercing so if you used the SMG vs them it'll take a lot of bullets but others can kill them really quick. I know its not obvious at all right now so you might have missed it, but if you hover the cursor over the guns in the UI to the left you can see their stats (AP for armor piercing). And if you stand on top of a dropped gun you'll see its stats after a moment, can also compare stats if you hover at the same time.
I threw in the score at the last minute so I can't say I'm too surprised its bugged somehow, thanks! Tweaking maps and enemies is something I'm expecting do to constantly so I'll look into it all. Hearing thoughts about enemy density and such is good because I think I've been playing so damn much I can't really tell myself - it all feels so easy to me.
But one tip is to use the shield gun when you feel overwhelmed sometimes, it can have a lot of utility. Its short range attack is pretty crappy except for pushing people away, but it can pretty easily destroy walls so you can make new passages if you need to. It also has a secondary fire mode, RMB, that protects you from incoming shots.