My my iPhone 6s might be slowing down, so this might not be a problem, but with the concentration test, the ball goes so fast that you have to tap when he’s hitting the ball, so when the ball slows down, you can’t react in time and you will hit early, and if you tap again, you will hit late, so you can’t recover (sometimes you can, but not all the time).
With the eyesight test, you have to replay levels you already beat, and there is a long pause between each level, so it’s a huge waste of time. This can easily be fixed by having the table shrink while you are playing and be scored in decimal size of the board instead of levels (rounded integers). Also each level is 3-7 hits (maybe longer or shorter, but these are the numbers I’ve counted), so if I can beat a level with 3 hits, why would I have to prove that I can see that well with 7 hits on the next one? Also this means that you can spend a long time on a play, and get the same score as when you spent a short amount of time.
The reverse test doesn’t have any issues. The only thing is, when you cut it close, it looks like the ball is going through your paddle. Maybe I just don’t cut it close in other modes because it is easier to react faster in them.