One of the issues I've been faced with are accessibility issues. One of the dudes who played the game happened to be color blind, and so was having a hard time distinguishing between the yellow and green circles. Since being able to tell these apart is important to gameplay, I had to think up a way to make it easier for the color blind folks. What I did was simply make a keyboard shortcut that makes a small letter "G", "Y" or "R" show up in the middle of a circle in a high contrast color. Should make things a little easier.
Also, I wound up inadvertently catering to lefties. The keyboard shortcuts for rotating left and right are the arrow keys, whereas placement of atoms is with the mouse. If you happen to be a rightie, like me and about 90% of the rest of the world, this is a might clumsy. So I doubled up the keyboard shortcuts, so that Z and X also rotate the atom.
It was also suggested to me that for the middle and right mousebuttons to do rotation. I will not be doing this, as I believe that if one CAN write a game that can be played solely with a single button mouse, then one SHOULD write the game that way. Since FSP also can generate files for standalone Mac players, I see this as a Good Idea.