Thanks a lot! I'm glad you enjoy it!
For making good 3d looks you should have just great 3d assets :) The hardest task is to imagine how the level will look even on a piece of paper. Also, before I used Unreal more, maybe it helps :)
For me, the difficulty is making a nice 2d game :D
Yes, the big ball is slow because it should feel like a big heavy ball. Maybe I was made so much heavy :D