The prototype is great. Even though the game isn't ready, the gameplay is so fun that it's hard to stop playing. In addition, it is a ready-made educational material for schoolchildren:)
I would note one drawback. The necessary control accuracy is not provided by the sensitivity of the keys. In some cases, it turns out that the player has already solved the intellectual problem of calculating the trajectory, but he is forced to suffer for some time with short button presses.
There is also a note that does not apply to the game itself. It seems to me that you did not choose the most successful settings for full-screen mode when placing the unity game on itch.io.