This game is a ton of fun! I now want to install it on my phone. I have a little advice. I think you should stick with this game. With some changes, I would drop a couple of bucks to have this game on Steam. 1) Give visual feedback (maybe make the color change every 10-20 rings?) This would give a sense of progression. 2) Probably music. I personally don't listen to game music, but some people do. Something with a heavy beat (check out super hexagon) 3) QWEASD is a bit awkward. Maybe arrow keys (left+up = top left?) or use the mouse (drag or maybe just swipe with mouse.) Num. pad might actually wok too
Overall, this is great. Keep up the great work. This could be something great!