A Java Applet by Doug Lea. Source java code is here (also zip file version).
Duplicate: Choose a tile, and duplicate it on any empty adjacent (including diagonally adjacent) square. All adjacent opponent tile will be flipped to your color.
Jump: Choose a tile, and move (not duplicate) it on any empty square two cells away. All adjacent opponent tile will be flipped to your color.
Pass: You can only pass if you have no available moves. (Although this version lets you pass whenever you want).
When you click on a tile, the available destinations are highlighted. Click on one of them to make the move. Or you can click Cancel to choose a different tile instead.
You can click on Auto, to have the computer choose a move. This is implemented via a search that can be adjusted to look ahead multiple moves (up to 8). Use the ++Level and --Level buttons to adjust this. Lookaheads greater than one are pretty slow, and greater than 3 are unbearably slow. You can make the computer stop searching by clicking Cancel (at least sometimes! For unknown reasons, in Netscape-2 on Solaris, mouse clicks and keyboard presses usually seem to be ignored during the move search.).
The Score listed at the top is just the difference in the number of tiles held by the current player and the other player.
I wrote this applet after helping my son Keith trying to beat this game for a few hours. While the game is sorta fun for a few hours, it occurred to me that it would be both faster and more fun to write this program than to spend many more hours trying to figure out good strategies. (In fact I still don't know of any good strategies; the move finder just uses blind search, which is why it is so slow -- much slower than the one in T7G.) And given that I was writing it in Java, it was almost as easy to make this into an Applet as not.
We beat the 7th Guest using lookahead level of three. The game took about an hour. (Actually, a lot longer, since, among other things, I didn't yet have an Undo feature, and neither does T7G. We kept making mistakes telling each other on the phone (from office to home) where our moves were.) Afterwards, I made the game a bit more usable, and put together this applet page.