Taps are easier to tap!

Previously the taps must be clicked exactly on their volume. This was almost impossible if you use a little screen (like an Android device) unless you use the zoom slider. Using the zoom slider was cumbersome, so I found a universal way to widen the radius. I used unproject_position() and OS.get_screen_dpi() for accepting the click (or tap) in a range of 1 inch. It works well; the arrows retain their range, which is not so big but doesn't interfere with a click on a tap.