RaiseChess strategy

What face-down pieces and chips change in a game of chess. First notes to the v0.5 rules – not part of the rules: the game is new and its strategy is still taking shape.

The deal: what your hand is worth

A face-down piece is worth 4.2 points on average: queen 9, rook 5, bishop 3, knight 3, pawn 1, each with a chance of 1/5. The piece it replaces is worth 2.6 on average: eight of the 15 possible squares hold pawns. So the deal adds almost 5 points of material to each side on average.
The difference between the sides matters more. With three face-down pieces each, in 55% of deals one side starts ahead by 6 points or more – more than a rook. Equal material at the start comes in about one deal in ten. With four or five face-down pieces the spread is wider still.
At least one queen in the hand: almost half the deals (49%). Three pawns: one deal in 125.
Material is not everything. A queen on the first rank takes a while to come out; a queen on the second rank, in a pawn's place, is open from the first move. A pawn on the first rank is weaker than a normal one: it only moves one square.

Preflop: when folding is cheap

To play, Black has to put 1 more chip into a pot of 3. The call pays if you win more often than one game in four. A hand clearly worse than average is better folded at once: you lose one chip.
Before the first move you see only your pieces and your opponent only theirs. A preflop bet is a bet on your own hand: the more its material beats the average (12.6 points for three face-down pieces), the readier you should be to raise.
A raise with a weak hand is a bluff, and it works: your opponent does not know what you hold either.

Reading: every move is a tell

At the start each of your opponent's face-down pieces can be any of five types; three together make 125 equally likely deals. A knight's move gives the knight away. A diagonal move rules out the rook, the knight and the pawn. One square straight ahead leaves the queen, the rook and the pawn.
While a piece stands still it can be anything. Move face-down pieces with moves that fit several types. The online version marks such a move with a dot: "the move keeps the secret".
The reverse is true as well: an early queen move across the board gives your opponent exact knowledge. Sometimes that is right, to win material for instance, but information is part of the stake too.
Read the bets as well as the moves. A big bet right after a move that revealed a queen says one thing. A big bet with pieces that have shown nothing yet may be a bluff.

Betting during the game

A bet before your move is made on incomplete information: you know your own pieces, the position and what your opponent has shown. The best time to bet is when the edge is clear to you and not yet to them. Once it is clear to both, they simply fold.
A fold costs only what is already in the pot. If the position is lost and your opponent bets, folding at once is cheaper than calling and losing.
The pot grows with bets, not with moves. A game in which nobody bet can be lost for the blinds alone.
No-limit betting, up to all-in, is the short stack's main weapon. Once the blinds are high, a bet of the whole stack makes the opponent decide the game at once.

Showdown: which move you are playing towards

In the showdown version the game ends with a material count after move 20, 30 or 40. The nearer that move, the less a positional edge is worth and the more material is.
When ahead in material, equal trades help: they do not change the count and leave the opponent fewer pieces to come back with. When behind, trades hurt – you need material or mate.
A captured face-down piece is turned over. Taking one is also a way to learn what your opponent held.
With equal material the pot is split; the odd chip goes to Black.
In the play-to-mate version there is no count, and the game is closer to ordinary chess: material matters as a way to mate.

The match, the blinds and the clock

A match is won with chips, not games. Losing several small pots and winning one big one is a normal way to win.
Rising blinds force play: folding preflop gets dearer over time, and a short stack has to look for a spot to go all-in.
With a clock each player has their own time per game, spent on moves and on answering bets alike. A bet when your opponent is short of time makes them decide fast.
You can resign at any moment, and the pot then goes to your opponent. Playing on without betting is never worse: you can always fold to a bet and give up the same pot. So resigning makes sense when it saves time – on the clock, or in a match with rising blinds.