I can confirm this as a usability bug.
** Changed in: gnome-sudoku (Ubuntu)
Severity: Normal => Minor
Assignee: (unassigned) => MOTU
Status: Unconfirmed => Confirmed
** Attachment added: "Updated .desktop file"
http://librarian.launchpad.net/2260506/gnome-sudoku.desktop
--
Poor tooltip
https://launchpad.net/bugs/35239