The chessboard with initial arrangement of pieces is illustrated on the above diagram. The files are a, b, c, d, e, f, g, h, and the equivalent of the squares of the 8x8 chess are 3D quadrangles. The game is played circularly. The frontier between the two opponent players is not a line (like the usual 8x8 chess) but the center O of the great circle (C).
Pawns move forward through its file, from one 3D quadrangle to the next 3D quadrangle, and once reaching the center O, can move along that file and go through the 3D quadrangles of that file of the opponent fields, or move along another file. At the start of the game, pawns can optionally move two 3D quadrangles at a time.
Example: e2-e4, e4-e5, e5-e5 (here the pawn continued moving along its file e, after crossing the center point O).
Example: e2-e4, e4-f5 (here the pawn changes direction after crossing the center point O and is moving along the file f on the opponent fields. The ROOK moves circularly from a 3D quadrangle to another 3D quadrangle, or radially.
Example: Ra1-d1, Rd1-d4, Rd4-d6 Remark: all the pieces must cross the point O in order to reach the opponent fields. And the line A B (or the horizontal diameter of the circle) represents a barrier. Example Ra1 cannot directly cross that line and move to quadrangle h8. Similarly this applies for Rh1 which cannot move to a8. However, when a piece reaches the point O, it can change direction and take any other file on the opponent fields.
Example: Ra1-a4, Ra4-e6 (here the Rook on the file a has changed its direction after reaching the point O and took the direction of the file e. This applies for all the other pieces.
The Knight moves like the Knight of the usual 8x8 chess.
Example: Nb1-c3, Nc3-e4, Ne4-d6, Nd6-c8, etc... But if the Knight is on g1 he cannot directly cross the line and go to a6, he must cross the point O in order to pass to the opponent fields. The Queen moves like the Rook or diagonally from quadrangle to another quadrangle.
Example: Qd1- b3 (diagonally), or Qd1-f3 (diagonally). The King moves like the Queen but only one quadrangle at a time. Castlings are done like those of the 8x8 chess, and the prise en passant is still valid.
Example: if white pawn is on the quadrangle c3 and a black pawn on d4 moves to d3 then white pawn can capture it en passant.
This three dimensional circular chess is playable like the usual 8x8 squares chess, except that the frontier line is now transformed into the center point O, and all the pieces have to cross this point in order to move to the opponent fields. The equivalent of the squares of the usual 8x8 chess become 3D quadrangles. The pieces moves look like moving along acylindrical tunnel, and towards an infinite point O. This is why this new game can be 3d Circular Chess and also it is perspective.