Great feed back! A couple of things. Sanics acceleration was designed to be able to go quickly however, I also made it so subtle movements are possible. In later stages bursts of speed are needed to make it across safely without being hit but subtle movements are needed in the late stages for avoiding properly. In terms of sanic falling with gravity I did make it so that it was very subtle to encourage moving instead of standing still but I'll consider removing that if it helps people.

Emeralds are not only obtained by rng. You can force emeralds out from being hit and collecting 300 rings. The highest scores are not due to luck they are actually from skill of not being hit and using super sanic effectively. You actually cannot get the highest scores on the board without really dodging the missiles and you'll notice in several playthroughs, while you might be astronomically lucky once you'll never be able to progress as far with pure luck alone and also you have to use super sanic in a skilled way being sure the clear the top most rings to put yourself in less dangerous situations as the game progresses.

The rings at the top are actually able to be obtained without being hit. While it seems they are at the very top and its more dangerous its also true that the missiles do not spawn directly above the rings. They actually spawn a set distance away from the rings off screen so its actually possible to safely get the rings before they actually come into a place where they can hit you. I've balanced it so its possible to do this all the way up until wave 150 in which only then is it actually nearly impossible because its mostly to force the user to lose at 150.

Input lag might be unity webplayer. If there's any input lag it shouldn't be present. Unfortunately I just recently found that unity webplayer has a lot of problems that I am trying to solve however some issues just have no solution other than porting the game to a totally different program language.