Thanks for checking out my game and for the kind words!
Haha, I don't think there's any real trick to it! It's just timing shots precisely and, ideally, trying to do it in one uninterrupted combo (getting a successful hit within 3 seconds of the last one). Scoring may be too biased towards chain vs individual hits, but I really wanted to reward that.
As for "zen mode", that I'm really glad to hear! I really need to concentrate to do well and yeah, you enter this flow state when you try to push for high score. Although I'm wired in a way that once I make a mistake, I'm very likely to do very badly for the rest of the run :D