I love the game! I love the idea of essentially casting spells with a gun. The mechanic reminds of of Magicka, which was a game I loved. I think there's a lot of potential here. It's also super polished. I'm very impressed. It was running very slowly for me on web though, unfortunately, so I didn't get to really experience it like I'm sure you intended.
Someone mentioned that inputting builds becomes tedious after a while. Maybe creating bullets gives you an entire magazine of them (5-10 rounds?), instead of just 1 bullet?