p.boxed
  | Your moves are decided by the opponent, to a square that you choose.

p.
  At each turn you must first play a move with opponent's pieces to the
  marked square, and then play a move freely with your pieces.
  The target in the first part of the move is indicated either by a colored
  discus for an empty square, or by a colored piece for a capture.

p.
  Exceptions: the first move of the game (which just mark a square), and a
  move which captures a king don't have a second part.

p.
  No check or checkmate, one wins by capturing the opponent's king.
  There is no castling.

figure.diagram-container
  .diagram.diag12
    | fen:rnbqkbnr/pppppppp/8/8/8/5g2/PPPPPPPP/RNBQKBNR:
  .diagram.diag22
    | fen:rnbqkbnr/pppppppp/8/3G4/8/5P2/PPPPP1PP/RNBQKBNR:
  figcaption.
    Left: White plays 1.Nf3.
    Right: Black executes 1.f3 instead, then plays 1...d5.

h3 Source

p
  | The 
  a(href="http://www.pion.ch/echecs/variante.php?jeu=ambigus")
    | rules description
  |  by the author of this variant, which is also playable 
  a(href="https://brainking.com/en/GameRules?tp=85") on brainking.com
  | .

p Inventor: Fabrice Liardet (2005)