The principle is simple, but the interface and everything is very neat/clean and works well. (Both visually and auditively.)

Just one question: is it normal that you can ‘hit’ multiple times in a row after the first correct press of Space, or is it a bug? You can go through the ceiling this way. ;)
(By the way, the Space key is not indicated, if I am not mistaken; you could add it on the game page or/and in the comments here.)

I think the game would have benefited from additional mechanics/surprises, so that it becomes more of a challenge. (Please tell me if I missed something and misjudged the game about this!)

You took the theme quite literally; I like twists, and I would not say your game  really provides one, but I do not think you were really going for one and played it safe. That’s fine. :) I just think it could have been more surprising.

My takeaway is that you concentrated on a simple idea, but really presented it in a clear and pretty form. This is very ‘polished’ (as the standard term goes), especially for a first game jam game (according to the game page). :) Well done (I myself have trouble polishing things XD).

I understand the idea, but your game is lack of tutorial, UI communication, mechanic.