I thought of something similar as a handicap idea a few days ago, where the weaker player gets a certain number of HP, and the stronger player can pass at any point in the game to remove one of them. The stronger player cannot win unless he wins on the board and has reduced the weaker player to 0 HP. One would also have to come up with some sort of mechanic to stop the stronger player from just winning on the board, and then passing during 1-2 point endgame to kill their opponent.
Perhaps the following formulation:
The weaker player has HP to start the game. Instead of moving, the stronger player can declare that the game will end within
x moves and write that declaration down in a notebook available for reference to both players, along with the current move number and the amount of hp that will be eliminated from that guess if right.
In order to calculate how much hp will be reduced by if and only if the game ends on or before the move predicted by the stronger player (the stronger player may be right in some predictions and wrong in others; they simply eliminate HP for the ones they were correct on, with no additional penalty or benefit from those they got wrong), take the difference between the current move (the move on which the prediction is made) (that move still counts as a move and not technically a pass, it’s just not on the board) and the move before which the game is predicted to end. If this number is smaller than the current move number, square it, divide by 1000 (or some other pre-agreed-upon constant; it doesn’t matter as long as you scale the initial HP accordingly), and that is how much HP (including fractional digits) will be taken off the weaker player if the game ends on or before the stronger player’s prediction. If the difference between the move on which the prediction was made and the predicted on-or-before end point is greater than the current move number, just square the current move number as before and divide by 1000 (as before).
Once per game, on their turn, the stronger player can declare the game over. Once this happens, if players can agree on dead groups, the game is scored normally. If players disagree on the status of groups, the game is still considered to have ended on the move the stronger player made the declaration for the purposes of removing HP, but the following procedure is used to see whether or not the stronger player’s assessment was correct.
The game is resumed according to the rules of whatever ruleset the players are using, and there are no more passes for HP reduction (though players may pass to resume counting normally), nor do the additional moves count towards extending the game beyond the stronger player’s predictions.
The stronger player wins if and only if all of the following are true:
- They have reduced the opponent to at or below 0 HP, only counting predictions which overshot or hit dead-on the length of the game.
- They have won on the board.
- If the game was disputed after the stronger player declared it over, the following are also true:
a) Every one of their stones which they claimed were alive, are either still alive, or occupied spaces which are now occupied by either friendly living stones, or friendly territory
b) Every one of their opponent’s stones which they claimed were dead, are still dead.
If the stronger player fails to meet any of these conditions, the weaker player wins.
These rules are meant to encourage HP reduction during the midgame, when it will likely be most exciting to see.