Suggestion:
Make it so that missed combos do not reset the combo count completely. Instead, have it deduct 2, 3, 4, 5, or even a percentage such as 1%, 5%, or 10%. (Or have a research that does something like this.)
As it is, I have to invest extra time and effort to more precisely ensure my pointer is correctly positioned. I can imagine that players with touch screens (i.e., on phones) get very frustrated with how imprecise tapping on the screen can be. It would also reduce frustration from mis-clicks and jitter (the very act of clicking makes my pointer sometimes move a small amount).