Ladder Game (Amidakuji)

How to play the ladder game

Set the number of players with the −/+ buttons, or type names into the Players box, one per line. The player count follows the names automatically, and pasted lists are split on line breaks or commas.

The ladder is built as you type. Tap a name at the top to watch that player travel down the ladder and open the result they land on. Reveal players one by one for suspense, or press Reveal all to draw every path at once.

• With Hide results on, the bottom slots show "?" until someone lands on them.
• Copy results copies the revealed results as "Name → Result" lines, ready to paste into a group chat.
• Hide again covers the same ladder again; New ladder builds a completely new one.
• With many players or a narrow screen, the ladder turns sideways and lists names top to bottom, so even 40 players fit on a phone without horizontal scrolling.

Auto-filled results and presets

There are three ways to fill the bottom slots. Win/blank lets you choose how many winners there are and fills the rest with blanks; you can rename both labels. Order creates #1, #2 … for everyone, for turn or presentation order. Custom takes one result per line; if you enter fewer than the number of players, the remaining slots are filled with blanks.

• Who buys coffee: one player buys, everyone else is safe
• Chore duty: one player on duty for up to 5 players, two for 6 or more (adjustable)
• Turn order: everyone gets a unique position starting from #1

Why this ladder is fair

In a ladder game, known in Japan as amidakuji, every rung swaps two neighbouring lines, so each player always ends at a different slot. But a ladder with randomly drawn rungs is not equally likely to produce every outcome: with few rungs, players tend to land at or near the slot right below where they started.

This tool works backwards. It first picks who lands where with a Fisher–Yates shuffle, so every outcome is equally likely. It then draws some random rungs at the top for looks and fills in the rungs needed at the bottom to produce exactly that outcome (using odd–even transposition sort). However many players there are, each player reaches each slot with probability exactly 1 ÷ the number of players.

The left-to-right order of the result slots is shuffled too, so while results are hidden, tracing the ladder by eye tells you nothing about who wins.

Share links and seeds: show everyone the same ladder

Each ladder is generated from a 128-bit seed made with your browser’s cryptographic random number generator (crypto.getRandomValues). The rungs and outcome come from the xoshiro128** pseudo-random generator running on that seed, so the same seed with the same names and results always produces the same ladder on any device.

A share link contains the names, results, seed and whether results are hidden. Post the link in your group chat before revealing anything and everyone can later open it and confirm the ladder was not changed. The seed shown under the ladder serves the same purpose.

A link only proves that this ladder gives this result. It cannot prove the creator did not make several ladders before sharing one. For bets that really matter, build the ladder while everyone watches and share the link right away.

Tips

A few ways to get more out of it:

• For group bets, keep results hidden and reveal one name at a time. The last two or three players are the most exciting part.
• For forfeits that hit several people (two out of four do the dishes), just raise the number of winners.
• Use Turn order for presentation order and Custom to hand out several different prizes.
• Names and settings are saved in this browser for next time and are never uploaded.
• To split people into groups, use the team generator; to pick one name quickly, try the wheel spinner.