This game is effectively a combination of a number of other
variants. Broken down, it is: Inchworm crowd-forming magnetic mutating
lunar-hallway exploding-Pawn chess
The initial board setup is identical to FIDE chess. The object of the game
is the same. The pieces are the same. And yet...
Inchworm
All pieces except Pawns move in two stages, extension and
consolidation. During extension, half of a consolidated piece moves
to a new square, capturing any enemy pieces on it. During
consolidation, half of an extended piece rejoins the other half. You
can leave a piece extended for as many turns as you like, and you can
consolidate a piece back to its original square, except during
castling. A King and Rook halfway through castling can remain in the
halfway state, but they cannot go back to the way they started. If the
King or Rook is moved or captured while in the process of castling, or
the halves of the King or the square between them is threatened, you
lose. When you capture half an extended piece, the other half
disappears as well.
A piece may move onto and off of squares occupied by other friendly
pieces. However, they may not move through them (except the Knight).
Additionally, groups of pieces that are on the same square may move as
a crowd. The crowd may move to any square reachable by the normal
movement patterns of any of its members, or to the square containing
the other half of an extended piece it contains. Only one member of
the crowd needs to extend or consolidate (or none of them if the crowd
contains a Pawn), though any of them can if they wish to (except
Pawns). If the crowd contains any half pieces, it can move to the
squares they could move to if they were whole pieces. A crowd can
consist of all the pieces on a square, or only a subset. It may
sometimes occur that by moving a crowd you consolidate some pieces and
extend others. Crowd movement sometimes puts Pawns on the first
rank. They can move forward one two or three squares, and are subject
to en passant when doing so on any of the squares passed over or
vacated.
When a piece (or crowd) moves (or extends, or captures (or both)), all
pieces reachable by a Queen's move from the square that was moved to
are subject to a magnetic force. Friendly pieces are attracted, and
move to squares neighboring the moved-to square. Enemy pieces are
repelled, and move away as many empty squares are available in that
rank, file, or diagonal. If multiple pieces are on a square, they all
get moved as a crowd. Magnetism also sometimes puts Pawns on the
first rank.
When capturing, the capturing piece becomes the type of piece that was
captured. If a crowd captures a piece, they all turn into that type
of piece. If a piece captures a crowd, it can turn into any kind of
piece in the crowd. If a crowd captures a crowd, all the pieces in it
get to decide individually what type of piece they turn into.
Consolidated pieces turn into consolidated pieces, extended pieces
turn into extended pieces. Pawns turn into consolidated pieces. When
turning into Pawns, both halves of an extended piece turn into
individual Pawns. Consolidated pieces turn into two Pawns, both on the
captured square. Pawns that turn into Pawns turn into one Pawn
each. There's no non-awkward way to word that.
To one side of the board is a strip of eight imaginary squares called
the lunar hallway. These squares are considered to be connected
orthogonally, diagonally, and by Knight's moves, to the squares of the
hallway that neighbor them.
At the beginning of the game there is no way to get to them, but on
each turn before moving, a player may link an unlinked square of the
hallway to a square of the same rank as it on the chessboard. The two
squares now function as though they were the same square. Pieces on
one are also on the other. You may not link squares containing enemy
pieces.
When you move off of a linked square, you can emerge onto the board or
into the hallway, but not both. When you move through a linked square
starting on the board, you can end up in the hallway, and vice versa
(Knights and crowds making Knight moves are not considered to move
"through" any squares at all, they just move "over" them).
You can move through multiple linked squares this way on a single
move. A Queen, Rook or Bishop (or crowd containing one of these) can
enter the hallway from the board, go down the hallway a few squares,
and emerge back onto the board heading in a completely different
direction all in one move. Pawns continue to follow their normal
array of funny little rules while in the in hallway. Note that the
diagonally connected nature of the squares means a Pawn can capture to
the square in the hallway directly ahead of itself. Pieces only in
the hallway will not be affected magnetically by pieces only on the
board, and vice versa. Pieces moving under magnetic influences that
pass over linked squares will not transfer between the hallway and the
board.
When all squares of the hallway are linked, players remove links at
the beginnings of their turns instead of adding them, until the
hallway is completely unlinked again. Then they go back to adding
links, and so on. When unlinking an occupied square, you get to
choose which side the pieces end up on. If there's more than one you
can leave some of them in the hallway and some on the board.
Exploding-Pawn
Every time a Pawn is moved, alone, as part of a crowd, or
magnetically, it has a 1 in 12 chance of exploding, destroying all
pieces on its square and the 8 around it. (You have a 1 in 12 chance
of rolling an 11 or 12 on two six sided dice, if that's what you're
using). The threat of Pawn explosions does not factor into check.
Check
Just use your common sense here. Checking rules don't really change
the game so I won't bother enumerating them.
Pawn Promotion
Pawns promote to consolidated Queens, Rooks, Bishops, or Knights. A
Pawn promotes at the end of the turn it reaches the 8th rank (assuming
it doesn't explode).