Fun concept. I think there needs to be bit more helping hand to the player. Two major ones:
A line showing the potential trajectory of movement. That way i can be more strategic in my plan, otherwise its very random and a crapshoot if ill bounce right.
The other is clear indication which walls are changing and which ones are not. Because there are walls that don't change witch each bounce and some that do, but they both look identical
Can see potential there