De Vasa's chess is a hexagonal chess variant played on a 81 hexagonal cells board.
The board is made up with 9 diagonal files ('a' to 'i') of 9 cells.
Each player commands 18 pieces
Moves 1 step forward to an adjacent cell (2 steps possible if first move)
Captures forward in diagonal i.e. similar color cell (see red circles below).
2 steps move for pawns (start): yes.
"En passant" capture: yes.
Stalemate is not a draw but is counted less than checkmate.
Castling: yes.