As someone who played every entry in the GemCraft series, i was little disappointed at first, at one point in the Game everything starts to feel like a grind, most levels aren't difficult, just build your little beat it all setup and call waves early and upgrade you area of death. It gets more difficult as you unlock more difficulties, but personally i recommend people to play it in Iron Wizard mode, less options, no going back to get stronger, just more streamlined and just the right amount of challenge.