Double Move One Time Each Go

This is a Go variant intended as a teaching tool for noticing ko threats.

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Play regular Go with any normal board size and rule set, plus this special rule:

 Once per game, each player may say before their next play "My double move, you must pass."  The opponent must pass their next turn.

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That's it! You'll note that this can be played on a vanilla online Go server, by prior agreement of the players.

Unless I've misunderstood something very basic, your opponent's "double move threats" are exactly the same as their ko threats. Unlike regular Go, where big kos just don't happen too often in novice games, in this variant, you are guaranteed that each player will have an opportunity to follow through on one ko threat per game.