Falling Balls is an avoidance game: obstacles descend the screen and you steer left and right through the gaps. It accelerates continuously, so the gaps get harder to reach as your reaction time stays the same.
It's an old and reliable arcade shape — one axis of movement, one thing to avoid — and it works because there's nothing between you and the failure but attention.
Yes — the descent speeds up continuously, so the same reaction time covers less distance as the run goes on.
Watch the top of the screen rather than your character, and stay near the middle where you can reach a gap on either side.
Yes — tap or drag. Nothing to install.