Sorry I'm late, but thanks for the extensive response! I should probably clarify a few things about the radar. For one, it actually can pick up on any emerald piece at a given time; the icon just indicates whichever one you're closest to. The appearance and color of the radar is something I've already changed and will be implemented in the next update, though it's worth noting that even as it currently is, the radar's beep rate will speed up as you get closer to an emerald, much like in the Adventure games. I assume that would be enough accommodation for those with color blindness, but I'm not certain. On that note, the keys and doors already have different shapes, though perhaps I could have made that more obvious.
I've received a number of comments about the speed being too low, so that will be tweaked in the next update. Though if you see this, I am curious, to what extent do you think it should be buffed? I don't want the control to be so fast that it becomes imprecise.