The patterns and slowdown are really cool mechanics. Kind of reminds me of Youmu from Touhou 7 : D
The controls were a bit hard to use, I think using the right mouse button for slow down would have made it more user friendly. I also would have made the hitbox of the player quite more tiny. It is rather uncommon that the entire sprite is the hitbox, and the patterns feel like they weren't made for this type of hitbox.
Overall, I think this was quite fun though, definitely a good base for something bigger! : )