Choose house rules

Start from a preset

HITOTSU_CLASSIC deals seven cards, with no stacking, jump-in or seven-zero swaps, and challengeable Wild Draw Fours. HITOTSU_PARTY deals five, stacks draw cards, allows jump-in and seven-zero hand movement. Both are native HitotsuOptions objects; copy one before changing a field.

import { HITOTSU_PARTY, readHitotsuOptions, startHitotsu } from "@johnmorrisdotca/hitotsu";

const rules = { ...HITOTSU_PARTY, jumpIn: false };
console.log(readHitotsuOptions(rules));
console.log(startHitotsu(200, ["Aki", "Ben"], 42, rules)?.size);

{
  stacking: 'any',
  jumpIn: false,
  sevenZero: true,
  drawToMatch: false,
  wildFour: 'challenge',
  deal: 5
}
200

Match length is separate

The first argument of startHitotsu is 1 for one hand, or 200 or 500 points. Choosing party rules does not itself change that argument. The browser table and builder supply their own setup defaults.

Read untrusted settings

Use readHitotsuOptions for received objects. It checks the full shape and supported values. Move shape validation is separate from move legality, which playHitotsu checks against the current game.