Let's return to the suggestion about conditional moves/lines:
Originally Posted by sakki
A suggestion to speed up games: if the next move of your opponent is forced or really obvious, why not include that and your next move in your reply. For example,
1. e4 e5
2. Nf3 Nc6
3. Bb5 d6
Now white plays 4. Bxc6, so why not say "4. Bxc6, if 4... bxc6 5. 0-0".
I guess this is common practice in correspondence games.
Imho conditional lines (CLs for short) can be set up in spoilers so that they follow the same algorithm as on chess.com.
Originally Posted by YouKnowWho
In short, because observers can see all texts of both players, they're encouraged to voluntarily do the 'arbiter' job of checking and relaying conditional moves (CMs for short) that chess.com's correspondence server would do automatically.
0. Assume that Black wants to set up a CL: 1. f3 (f4) e5 2. g4 Qh4#, meaning the following: 'if White plays 1. f3 or 1. f4, then play 1... e5 for me automatically in my absence, plus, if my first CM (1... e5) gets triggered and then White plays 2. g4 (either manually or conditionally too), then automatically play the 2... Qh4# CM for me too'. Obviously, every White's move should be followed by not more than one Black's response.
1. He writes the CL into a spoiler that is specifically marked as containing CLs and can, as usual, be read only by himself and observers but not by the opponent.
2. White eventually posts his pending move (Black might be sleeping or otherwise AFK or busy at this time).
3. Any (preferably first) observer who reads the thread after that looks up Black's preceding conditional spoiler (CS for short) and, if one of the White moves anticipated there matches White's actual move, the observer announces Black's CM. Otherwise the observer announces that the actual move doesn't match any of the CLs and it's now Black's turn.
E.g. in our case, if White has played 1. c4, no extra move is made, it's Black's turn and he must post a move himself (revisiting the thread).
If White has played 1. f4, an observer announces the CM 1... e5 is auto-played for Black, but doesn't disclose any other/further moves/lines from the CS, and it's again White's turn.
If White has written a CS for his 2nd move, the same observer should check whether it matches Black's 1st CM. If White has written a CL '1... e5 (e6) 2. g4', then g4 gets played for him automatically and then immediately 2... Qh4# is played also automatically.
If White hasn't written a CS at all or the observer finds that White didn't anticipate 1... e5, White must now make a move himself.
If he now plays 2. fxe5, an observer (possibly another) sees that White's second move predicted in the spoiler doesn't match it. Black then must make a normal second move himself.
If White plays 2. g4, an observer who looks the spoiler up finds that it matches the actual move and announces 2... Qxh4#.
Note that, even if no observer has looked the spoiler up between White's move and Black's return to the thread, Black can post the move himself regardless (I think he should be given the right not to announce whether White's move was anticipated in the CS - after all, it's observers' fault that none of them has looked up and played the move earlier if it happens to be conditional).
However, a 'semi-touch-move' rule should apply: if White makes one of the moves predicted in the CS, then Black can't make a move other than the one he specified in the spoiler, even if no observer has dug it up.
Of course Black has the right to cancel a CS and/or to post a new/edited CS at any time before White plays his move. The last posted CS for a certain move (say, move 15) prevails until White makes that move (move 15); if White's move triggers a CM, then the content of the CS is carried over to the next move (move 16) with the actual 15th White's and Black's moves deleted from the CLs (as they've already been played).
Let me give a more extended example of how a conversation may unfold.
W = White, B = Black, O1 (O2) = Observer #1 (#2)
W *** gets up ***: 1. d4.
O1 *** reads both spoilers ***: 1. d4 Nf6 2. c4 e6,
W is to make move #3.
*** goes to bed ***
W: 1. d4 Nf6 2. c4 e6 3. Nc3.
*** goes to work ***
O2 *** reads all the spoilers and applies Black's 1st spoiler and White's 2nd ***: 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2,
B is to make move #4.