Extra moves

In chess, you get one move and then it's their turn. That single rule is why most of the game's tactics exist: the fork works because you can only save one piece; the pin works because the pinned piece can't move and something else can't move either; checkmate works because the king gets one move and every one of them is bad. Give a player two moves in a row and all of that bends.

Built Deck has five cards that do exactly that, at five different prices. Here's what a second move is actually worth, what the cards charge for it, and how to turn the extra tempo into something that ends the game.

The five cards

Move Again costs one Braincell and gives one additional move this turn. It's the cheapest tempo in the game and the one you'll see most.

Double Time costs three and gives two additional moves, so three in the turn.

Blood Oath costs one Braincell and one of your own pieces: sacrifice a piece, then take two extra moves. The Braincell price is low because the piece is the price.

All In costs two Braincells, a card discarded from your hand, one of your own pieces sacrificed, and a captured piece handed back to your opponent. For all that, three extra moves: four in the turn.

Prisoner Exchange costs two and a give-back: return your opponent's most recently captured piece to the board, and take one extra move. It's a regain card that happens to carry tempo, and the piece you return is the price.

Two things are the same across all five. Each extra move is a full, legal chess move, made by any piece you like, with the same rules about check that any move has. And none of them gives you another card. The one-card-a-turn rule still stands, so the extra moves have to be made with the pieces as they are.

What a second move does to tactics

The fork stops working against you. A knight forks your queen and rook; you move the queen, and with Move Again you move the rook as well. The fork cost your opponent a move and bought them nothing.

The fork starts working for you twice over. A knight that forks two pieces normally wins one. With an extra move it takes one, then takes the other before your opponent has replied.

A piece can move twice. A rook can go to an open file and down it in one turn. A knight can make two hops, which reaches squares no knight reaches in one. A bishop can switch diagonals and then act on the new one. The piece arrives where your opponent reckoned it couldn't for another turn.

Exchanges happen in one go. Capture, and when they'd normally recapture, you've already moved the capturing piece away. Or capture, and capture the defender too, so the recapture never comes.

A pawn can run. Two pushes in one turn, three with Double Time, is a pawn halfway up the board before anyone's had a chance to stop it. Tripping, which lets pawns move one extra square forward this turn, is a cheaper version of the same idea for a pawn you only want to move once.

And stalemate has a wrinkle. A stalemate only stands once the mover has no move left in the turn. If you've an extra move in hand and no legal move for it, the position isn't settled until you've nothing left to try.

Turning tempo into mate

The ordinary way to checkmate is to attack the king with one piece while others cover its escape squares, built up over several moves during which your opponent sees it coming. An extra move lets you build the net and spring it in the same turn.

The pattern to look for is a king with one or two escape squares and a piece of yours that could cover them if it had time. Move the first piece to take away the escape, then the second to give check. Your opponent never gets the move in between that would have let the king walk away.

A second pattern: the defended checking square. You want to put a rook on the back rank with mate, but a bishop guards the square. Take the bishop with your first move, land the rook with your second. In normal chess the recapture after the bishop would have come first.

A third, which Blood Oath is built for: sacrifice a piece as the cost, and use the two moves to punish the fact that the piece is gone. Sacrifice the pawn that was blocking your own rook's file; the rook now sees the king, and you have two moves to use that with.

The cards that change how pieces move stack with this. Queen Like on a knight plus Move Again is a knight that moves like a queen twice. Rook Like on a bishop plus Double Time is a bishop that hops onto a file and runs down it. The cost adds up (Queen Like is three and Move Again one), but a four-Braincell checkmate is cheap.

Reading the costs

The extra-move cards are priced so that tempo roughly costs a Braincell a move, with discounts for paying in other things. The question is what each other thing is worth to you.

Blood Oath's sacrifice is a piece. Early on, when you have a pawn that's doing nothing, that's nearly free. Late, with six pieces left, a piece is a quarter of your army. The same card is a bargain in the opening and a desperate measure in the endgame.

All In's four costs are each small on their own and heavy together. A card from hand means a card you won't play. A sacrificed piece is a piece. A piece handed back is one your opponent now has again. Three moves is a lot of moves, but the turn after All In you're thinner on every front. It's the card for the turn you've decided the game ends now, one way or the other.

Prisoner Exchange's give-back is the subtle one. The piece you return is your opponent's most recently captured, which you can usually see coming. If that's a pawn, you've bought a move for a pawn. If it's their queen, you'd better be mating with the move.

When not to play them

An extra move with nothing to do is a Braincell spent moving a piece you were going to move anyway. Hold Move Again until there are two things you want to do and one turn to do them in. That turn comes most games; the card is worth more on it than on a quiet turn where you're developing a knight you'd have developed regardless.

Don't spend extra moves on a frozen or stuck position. A frozen piece still can't move, however many moves you have. A piece pinned to your king is still pinned on the second move.

And check your own king between moves. Each move has to be legal, so the first move can't leave your king in check and neither can the second. A plan that leaves a check hanging after move one won't get to move two.

The defender's side

Facing a player who holds extra-move cards, the chess changes too. A piece one move from safety is two moves from safety if they have Move Again, so threats you'd normally meet next turn have to be met now. The square beside your king that's covered by one piece is covered by nothing if that piece gets taken and the king gets attacked in the same turn.

The defense is the same as it always is: fewer loose pieces, a king with more than one escape square, and a Flash Shield or Flash Freeze in hand for the turn the extra moves come out. A frozen piece can't make the second move either.