Yinsh is probably the easiest of the GIPF games to learn. The
goal of the game is to capture three rings of your own
color. You first place five rings on the board,
then each move pick a ring to move. Moving a ring leaves a
chip behind, and changes the color of all the chips it passes
over. Whenever a row of 5 chips is created, they are removed
from play, along with a ring of the same color. There are a
few subtleties in the rules,
but that's the basic idea.
This looks vaguely similar to Othello, but it is much subtler because
removing the chips creates new open space, and removing a ring
(progress toward winning) weakens you.
The robots for yinsh are smart enough to win against beginners, but can
be beaten once you get used to the colors changing. Basicly
the robots are very good at keeping track of all the flipping, but
relatively clueless about overall strategy.