This satisfies my OCD.
It's really difficult to reach 50%, especially because it's hard to remember which sponges were placed effectively and which weren't (I had to take notes).
If the game, during the positioning phase, showed where the sponges were placed in the previous attempt, it would be much more enjoyable!
Additionally, I have the feeling that the percentage calculation isn't always accurate. I once got 52% with a placement that seemed to cover much less space than previous attempts.
In any case, it's a great idea that could turn into an excellent mobile game.