There are other Sudoku options here at TPFC, but not as lean and well-rounded as this one, IMHO; USB Sudoku executable is only 42KB and there's both an ANSI and a UNICODE version included in the download archive for you to choose. Coded in C(++), it can be played with either mouse or keyboard. It's advertised as pre-Alpha software, but it looks rather mature to me -- documentation excepted, but that's easy to overcome. So here it is...
http://sourceforge.net/projects/usb-sudoku/ wrote:
A very small executable for playing the original game of Sudoku. Created specifically for use from a USB stick drive. Completely portable. Completely green. Uses Bill Dupree's solver/rater. All generated games are guaranteed to have only one solution.
