That was nice so far. A message in the end would have been nice, to tell me that I lost now and that now the best timing would be to press R xD

It's a bit random. As LeslieLlama has already mentioned below, the pattern followed by the grey dots is not very clear, but was  fun.

This was really cute! definitely reminded me of the old Game and Watch stuff; I think going the extra mile and making the presentation emulate old liquid crystal screens with the graphics would really push this over the line for me; as it stands it's a fun, simple gameplay concept. 
A less abstract theme could also be a fun addition; a lot of old game and watch stuff had a idea or theme to give context to the gameplay, Fireman or Vermin come to mind. 
I didn't *quite* understand the pattern behind the grey dots movement, making that a little more clear would help as well I think
Overall good job! got a highscore of 23

I struggled to comprehend exactly what was going on (I've unfortunately never played game and watch), but I did really enjoy the music and presentation of the game! I think if you even put a little bit of instructions in the desc it would help a ton! Great job though on making a complete and appealing game!

Interesting