Hexxagon probably isn't one of the first games you think of when it comes to retro classics, but it was such a great game that I had to remake it in Flash. It's an adaptation of the board game Othello by the now sadly defunct Argo Games in 1992.
You play as the red diamonds and your opponent (either another player or the computer) plays as the blue globules. Your goal is to take over all the spaces on the board, and you do this by leaping into the spaces next to your opponent's pieces.
When you select one of your pieces, highlights of possible moves will be shown. The green highlights show where your piece will duplicate, the yellow highlights show where you will only jump. It's a good idea to duplicate as much as you can early on, and to spread around the board so you're not cornered.
It's not that complicated once you get the hang of it, trust me...
Legal notice: This game is an unofficial clone of the original Hexxagon game and is not endorsed by Argo Games.