Early game is challenging, keeping energy generation vs defense balanced took a few tries to get right. Mid game (up till about round 30) still takes management but is mostly just balancing adding weapons whenever the waves get past initial defenses to adding energy generation. Once you get to late game energy gen quickly outpaces spending ability and you're sitting there with 1000+ energy. I fell asleep around round 50 and woke up and apparently had lost at round 228. Would've lasted longer if I'd bothered with pathing, that was just with the waves following the shortest path but maxed out weapons.