Capatomic Random Chess

This variant combines aspects of both Capablanca Random Chess and Stratomic Chess. It retains essentially everything from Capablanca Random Chess except for the board size, but makes significant changes to how the missile piece inspired by Stratomic Chess functions.

Setup

One out of a few thousand possible starting positions for Capatomic Random Chess:

The pawns are always in the 3rd and 8th ranks, the major pieces (except the missiles) are always in the 2nd and 9th ranks, and the missiles are always in the two squares diagonally behind each king (in the 1st and 10th ranks). However, the ordering of the pieces in the 2nd and 9th ranks is intended to be chosen at random before each game, with the same restrictions as in Capablanca Random Chess:

1. The bishops must be placed on opposite colored squares; the same rule applies to the implicite bishop pieces: queen and archbishop
2. The king must always be placed somewhere between the rooks to enable castlings
3. All pawns must be protected by at least one piece

In order to accomplish this, one may use the following method (or any other effective randomization method):

1. Randomly select the queen or the archbishop to be placed first (2 possibilities)
2. Place the piece selected first on a randomly selected light square (5 possibilities)
3. Place the other piece on a randomly selected dark square (5 possibilities)
4. Place one bishop on a randomly selected light square (4 possibilities)
5. Place the other bishop on a randomly selected dark square (4 possibilities)
6. Place the chancellor on a randomly selected free square (6 possibilities)
7. Place one knight on a randomly selected free square (5 possibilities)
8. Place the other knight on a randomly selected free square (4 possibilities)
9. Place the king on the middle square of the three free squares remaining
10. Place the rooks on the remaining free squares
11. Fill the row in front of the major pieces with ten pawns
12. Discard the position and repeat steps 1-11 if there are any unprotected pawns
13. Place the two missiles on the two squares diagonally behind the king
14. Set up the pieces on the other side of the board to mirror the setup you just did (e.g. if the white queen was placed on a2, the black queen must be placed on a9)

Pieces

 Pawn - Same movements as in standard chess, but promotion rules differ slightly (see the "Rules" section).

 Rook - Same movements as in standard chess.

 Knight - Same movements as in standard chess, and can jump over (but not land on) irradiated squares.

 Bishop - Same movements as in standard chess.

 Queen - Same movements as in standard chess.

 King - Same movements as in standard chess, but castling functions slightly differently, and the king and the 8 squares around him (i.e., a 3x3 area centered on the king) are shielded from missile attacks. The shield moves with the king, and so moving the king will change which squares are protected.

 Archbishop - Has the movements/attacks of both a knight and a bishop.

 Chancellor - Has the movements/attacks of both a knight and a rook.

   Missile - Can move one square per move in any direction (just like the king) and can capture enemy pieces (and be captured by them), but can also instead be launched (an attack which consumes the missile) to any unshielded square on the board, including the square it is on (if it is on an unshielded square) and irradiated squares. In order to launch a missile, the square that a missile is on must not be currently threatened by any of the opponent's pieces, and at least one major piece (anything that's not a pawn) needs to have been previously captured by someone at some point in the game. This launching attack removes ALL pieces (both your own and your opponent's) in a 3x3 area centered on the square where it hits (with the exception of any squares shielded by a king). The attack irradiates the square that the missile was launched to, making that square impassable for the remainder of the game. Lastly, one or both of a player's missiles can optionally be brought along with their king when they castle if two conditions are met (see the "Rules" section).

Rules

Capatomic Random Chess differs from Standard Chess only in the ways which I have described above and below this section. All rules from Standard Chess that have not been touched upon in these rules can be safely assumed to apply to Capatomic Random Chess as well.

Castling
Regardless of the starting position, the white king will always end up on i2 when castling in the direction that would normally be kingside (to the right, from white's perspective) and c2 when castling in the direction that would normally be queenside (i.e., toward the a-file―the queen might not actually be on that side of the king). The same principle applies for the black king―castling queenside (O-O-O) will bring the black king to c9, and castling kingside (O-O) will bring the king to i9. In order to castle, the king's destination and every square of the path between him and that destination must have no piece (with the exception of the rook being used to castle) on it, must not be irradiated, and must not be threatened by any of the opponent's pieces; there also must not be any pieces or irradiated squares between the king and the rook, the rook's post-castling destination must not be irradiated or occupied (unless it is the king who occupies it), and the king must not be in check. And of course, just like in standard chess, you may not castle if you have moved either the king or the rook you intend to castle with earlier in the game.

Castling with Missiles
If the necessary conditions are met, a player has the option of bringing one or both of their missiles with the king when they castle. A missile can only be brought along with the king when castling if that missile has not moved in the game thus far, and if there is no piece or irradiated square between it and its destination or at its destination (if both missiles are being castled, then it does not matter if one missile is, on the turn when the player castles, in the spot where the other one will end up after castling). Both of these conditions must be met in order to bring a missile along with the king when he castles. A missile that castles with the king will always be in the same position relative to the king that it was in before castling. For example, if a player is playing as white and has their king on f2, a missile on e1, and a missile on g1, and then castles kingside (O-O), the king will be on i2 after castling, and if the player brought both of their missiles along, one missile will be on h1, and the other will be on j1.

Pawn Promotion
White pawns achieve promotion on the 9th rank, and black pawns achieve promotion on the 2nd rank. Pawns can be promoted to any major piece, including a missile.

Check Through Irradiated Squares 
Check cannot be given through irradiated squares, except by means of the L-shaped jumping attack possessed by knights, chancellors, and archbishops. It is therefore possible to use a missile's launch attack to block check or even to block what would otherwise be checkmate.

Missile Launching
You can only launch a missile when it is your turn, and you cannot launch a missile if you have made any other move that turn; launching a missile consumes an entire turn, just like all other moves do. You may launch a missile while your king is in check if doing so will remove that check (by destroying the attacking piece(s) and/or by blocking the check).

Last revised by Gaelyn Autumnsong.