Really interesting!
But maybe need a little more balance?
I tested some (but not sure)
AR:2.5energy/shot 12dmg
Launcher:15energy/shot 60dmg
Shotgun:12.5energy/shot (8 bullets) 12dmg/bullet
Sniper:20energy/shot 100dmg
Launcher is AOE so we don't consider about it now
So, AR 4.8dmg/energy Shotgun 7.68dmg/energy and Sniper 5dmg/energy
But in my opinion AR is the best weapon because it only cost 2.5energy per shot so when hit crystals it's very efficient.
Also, I test the upgrade (not sure too). The upgrade which shot the secondary bullet deal 80dmg. But seems no matter which weapon u use it deals 80 dmg so it behaves better when have a higher fire rate which is AR. Maybe the dmg should base on base dmg?
Shotgun and Sniper seems have little features too. With more pierces AR can use as a shotgun which even have a higher range. And with secondary bullet AR deals more dmg than Sniper sometimes.
Moreover, full health gives too much dmg bonus while low health gives so little. It's easy to keep full health and riskier when keep low health.
In my opinion, maybe every weapon needs its feature?For example, Shotgun can stun enemies when all bullet on it, add more small enemies (low HP but a lot) maybe good for Launcher? Or cluster bombs. Sniper can breakdown enemy's armor (It will be taken more dmg (from all weapons) after shot by sniper) (or just armor which decline dmg it taken which can be removed by sniper?), or maybe a sniper have 2 modes, tap can shot a normal bullet while hold on can charge a much powerful bullet. Also I think it should have more crit chance and dmg, and upgrades add more. Maybe it‘s better to use roller to zoom too?
And about multiplayer, it's discouraged when face a no one lobby. Also add a radar will benefit a lot I think (because often can't find my teammate especially they need help) . And a chat may useful? Or just some commands like "go here" "cover me " can make a good gaming experience.
And it may hard to understand crystal gives money? (After a long time I find out it XD). Maybe some beginner tutorial useful?
Anyway, it's a good game. The future is promising. Recommending it to my friends XD. Also want to know if more language is considered, I can't understand what proc means until now XD (I can help if Chinese localization is needed)