This reminded me of the really fun mechanic beat blocks in Mario games. I think what they did really well is clearly telegraph when the platforms would change:
Perhap using a clear beat in the background and or adding some visual indication of what will happen next, perhaps using a flashing or pulsing animation would help.
I found myself staring at the countdown and trying to move in my periphial vision. Also it was not always so clear when to jump as the countdown would show 0 seconds left for a certain ammount of time?
It's a cute game and I really hope you explore this idea more!