AGEIOU – the cosmic origin of chess

The board

  • The board is 10×10. From left to right each side lines up boat, Vertag, knight, bishop, councilor, king, bishop, knight, Vertag, boat, file for file. Each side's ten pawns start two ranks in front of the back rank, leaving an empty rank between. A pawn changes its look after a single step forward.

The pieces

The pieces are called tenats. Each is shown for the light side, then the dark side.

Moving and capturing

  • There's no check: moving your king into an attack is legal.
  • A king can't die while its side still has a bishop. When a king with one left is captured, the capturing piece takes the king's square, and the king teleports to the square of one of its own bishops. That bishop is lost. If it has two, the king's own side chooses which one.
  • On any turn, instead of moving a piece, the king can swap places with one of its own bishops, wherever that bishop is on the board. Click the king, then the bishop (marked with a dotted ring).
  • Pawns have no double step, no en passant, and there's no castling.

Portals

  • Instead of moving, a Vertag can start building a portal on the square it stands on. A portal leads to its exit: the entrance square turned exactly 90 degrees counter-clockwise about the centre of the board (seen with the light side at the bottom), the way the rays of the eclipse in the middle of the board curl. So the corners go round a1 → j1 → j10 → a10 → a1, c2 leads to i3, and around the middle e5 → f5 → f6 → e6 → e5. Every square has exactly one exit.
  • On the four centre squares the exit is right next door, so a Vertag there could also simply move onto it. In that case the dashed ring for building the portal is drawn on the Vertag itself: click the Vertag again to build.
  • Building takes 3 of that side's turns in a row (you can set it anywhere from 1 to 7 under Portals on the game pages; a change applies from the next game), and the portal only opens at the end of the last one. With 1 turn, it opens on the very move that starts it. On each turn after starting, the side chooses: keep building (the builder stays put), or make any other move instead, which abandons the portal. If the enemy captures the piece building it, the portal is lost too.
  • Portals are one way and stay for the rest of the game. Any piece of either side except a pawn whose move would end on a portal's entrance may end on its exit instead, and a piece already standing on an entrance may use its move to go straight to the exit. Pawns can't use portals at all: they can stand on an entrance, but they never travel through. Either way you just click the exit square, which is marked as a place the piece can move to like any other. A piece can't come out onto one of its own pieces; an enemy piece on the exit is captured.
  • While a portal is being built, its marks are faint and dashed, with the turns done (e.g. 2/4) on the Vertag's square. On the board, a violet whirlpool marks an entrance and pink ripples with arrows mark an exit. A square that is both the exit of one portal and the entrance of another shows the two marks together.

How a game ends

  • Capturing the enemy king wins once it has no bishops left.
  • A side with no moves at all loses.
  • A side that is down to its bare king hasn't lost yet: the game is played out until its king is captured, it runs out of moves, or one of the draw rules below ends the game.
  • The same position occurring three times is a draw. You can raise this (up to twelve times) under Draw rules on any game page.
  • Fifty moves by each side without a capture or pawn move is a draw. You can raise this (up to 300 moves) under Draw rules on any game page.