The buttons to change rows on the skillbelt could stand to be a little bigger. Especially on the enlarged UI, on which they are inexplicably not at all enlarged. They're kind of tiny, and it's a bit too easy at the moment to accidentally miss them and have the game think you clicked to move to the bottom of the screen (unless you take extra time to make sure the pointer is aligned just right; which isn't so bad the first few times, but gets annoying when you have to do it a lot).
