It may also work for other games where you can't seem to use a drawing tablet to play:

In the tablet configurations (as in, Wacom Preferences, or the ones you installed for your own tablet's brand), pick Mouse Mode instead of Tablet Mode and make sure to disable mouse acceleration; this will make the pen act more like a mouse and will enable for those with tiny wonky hands (such as myself) to score a half-decent score at this game. It's not a perfect solution, but it's still a workable one.

P.S.: If the symbols aren't being recognized when you draw them, draw them bigger! it helps a bunch.