Very nice !
Simple in the idea, damned effective in the realisation !
I could never have suspected that under such an epured window and a simple menu would hide a diabolic game. Very intense, you make the player be super focused for this small minute.
In my opinion it's really nicely made. Perfect music, nice and very simple graphism.
I guess the window size is perfect cause if you make it larger, it'll take more time to go from one circle to another. Same thing for the colors. That's a good idea to add some to keep the player entertained, but the grey one is probably the best, talking about legibility.
Nothing to criticize actually. Though, I guess the interest of the game is a bit limited :D ;)
8/10 and 5/5 (technically there's nothing to add here according to me)