Very interesting mechanics. Though pretty difficult for me.
I would say add ways to add nuances to game, rather than just being a reaction game.
For example, you can add changes to the game that change how it's play (like options to choose before playing):
Add two balls instead of one but they are slower.
Add laser beam occasionally spawns that can kill the player, but can also burn the balls
etc.
I think the core idea is okay, but you should try to build upon that idea