FYI the game crashes when trying to upgrade the highest tier (Demons O, Souls E, Worm C).
As for mechanics, the Waste resource is a pain -- especially since it's not clear that Energy gives you some until you actually unlock it. But even very late into the game, Waste is always the blocking material, and since there's no way to upgrade your ability to get it but the cost of using it increases, it's very frustrating to scale later game.
And one more bit of advice, change your numbers display. The early-game displays are extremely confusing (SpQi? QaTg?), so it's hard to tell what the numbers are. Later when you switch to E notation, it's much better, so why not just start with that, at least past T which is the last commonly-used notation.
Hope you add some new content eventually.