This 3D version of Othello was written by Ben Fry. The original board imaged looked very dark, so I've lightened it here for you.
You move first, playing the Black pieces.
You play a piece by clicking the mouse on an unoccupied square. This puts one of your pieces into that square. The idea is to trap one or more of your opponent's pieces between two of your pieces. Those opponent's pieces then change color to become your pieces.
When either you or your opponent cannot play another piece, the game is over. The winner is the one with the most pieces.
Click the speaker icon to turn the game sounds off and on.