The website type.method.ac has a kerning game, that feels awfully familiar, I'm sure I've played it before. (yes I have!) But I'm obviously a little rusty, so as I loaded up the site just to write about it, I lost 30 minutes of productive work-time just kerning type while mumbling "three quarters of the width of the lower case o", repeatedly, under my breath. Aaaah! You suckered me in! Us art folks simply can not let bad kerning stand. It must be fixed. So be warned if you have ADOCD, you will lose a lot of productive time here, time you could be spending kerning that headline. The site is very well designed so you can use your cursor (or finger if you're on a tablet), or the arrow keys to move the letters.