Sports Rules

Work an offside call through the published decision procedure — association football under IFAB Law 11, or ice hockey under NHL Rule 83 — and return every step, not just the verdict. Use this for any "was that offside" question in either sport. The two rules are structurally OPPOSITE and are routinely conflated, and there are four specific things that get answered wrong: SOCCER: 1. HANDS AND ARMS DO NOT COUNT, for anyone including goalkeepers. Only parts that could legally score are measured, and the boundary is the bottom of the armpit. This tool REFUSES to compute from an arm position rather than guessing where the shoulder was. 2. AN OFFSIDE POSITION IS NOT AN OFFENCE. It becomes one only with involvement in active play. Do not report "he was offside" when the answer is that he was in an offside position and uninvolved. `involvement` is REQUIRED once the geometry makes it decisive — the tool errors rather than assuming, so ask the user what the player actually did, and pass "none" if the answer is nothing. 3. No offside offence direct from a throw-in, goal kick, or corner. Absolute. 4. A DELIBERATE play by an opponent resets it; a deflection or a save does NOT. This is the distinction most arguments turn on. HOCKEY: 5. SKATES decide it. Not the stick, not the body. 6. Since 2021 a skate in the AIR above the blue line is still onside — the line is a plane, and ice contact is irrelevant. BUT this does not apply to tagging up on a delayed offside, where the skate must contact the line. Do not generalise the 2021 change to tag-ups. Input for soccer: positions along the attacking axis in metres, larger being nearer the opponents’ goal line — `attacker`, `ball`, `secondLastDefender`. Any consistent scale works; only the order matters. Optionally `restart`, `foremostPart`, `inOwnHalf`, `involvement`, `lastTouch`. Input for hockey: `rearSkate` in centimetres relative to the LEADING EDGE of the blue line, negative being the neutral-zone side. Optionally `skateOnIce`, `situation` (zone-entry or tag-up), and `stick`. Returns: a verdict of offside, onside, or no-offside-offence — three outcomes, not two, because "in an offside position but no offence" is a real and common answer — plus every step with the decisive one flagged, warnings, and a disclaimer. THIS IS NOT AN OFFICIAL RULING. Relay the steps, not just the verdict: in a real call the procedure is the easy half and the inputs are the argument. Do not quote IFAB or NHL rule text; it is copyrighted and this tool does not reproduce it.

{
  "type": "object",
  "properties": {
    "sport": {
      "type": "string",
      "enum": [
        "soccer",
        "hockey"
      ],
      "description": "Which rule book. The two are structurally opposite — do not mix them up."
    },
    "attacker": {
      "description": "SOCCER. Position of the attacker along the attacking axis, larger being nearer the opponents’ goal line. Any consistent scale; only the order matters.",
      "type": "number"
    },
    "ball": {
      "description": "SOCCER. Position of the ball, same scale.",
      "type": "number"
    },
    "secondLastDefender": {
      "description": "SOCCER. Position of the SECOND-last opponent, same scale. Usually the last outfield defender, since the goalkeeper is normally the last.",
      "type": "number"
    },
    "foremostPart": {
      "description": "SOCCER. Which part the attacker position describes. Passing an arm or hand is REFUSED with an explanation: only parts that could legally score count, and the boundary is the bottom of the armpit.",
      "type": "string",
      "enum": [
        "head",
        "shoulder",
        "torso",
        "hip",
        "thigh",
        "knee",
        "shin",
        "foot",
        "arm",
        "upper-arm",
        "forearm",
        "elbow",
        "hand",
        "fingertip"
      ]
    },
    "restart": {
      "description": "SOCCER. There is NO offside offence direct from a throw-in, goal kick, or corner. Always ask which restart it was before answering.",
      "type": "string",
      "enum": [
        "open-play",
        "throw-in",
        "goal-kick",
        "corner-kick",
        "free-kick",
        "kick-off",
        "drop-ball"
      ]
    },
    "inOwnHalf": {
      "description": "SOCCER. A player in their own half cannot be in an offside position.",
      "type": "boolean"
    },
    "involvement": {
      "description": "SOCCER. REQUIRED once the player is in an offside position — the call errors without it rather than assuming. An offside POSITION is not an offence; this is what turns it into one, and \"none\" is a common and correct answer meaning play continues.",
      "type": "string",
      "enum": [
        "none",
        "interfering-with-play",
        "interfering-with-opponent",
        "gaining-advantage"
      ]
    },
    "lastTouch": {
      "description": "SOCCER. A DELIBERATE play by an opponent resets offside. A deflection, a save, or a rebound off the frame does NOT.",
      "type": "string",
      "enum": [
        "team-mate",
        "opponent-deliberate-play",
        "opponent-deflection",
        "opponent-save",
        "rebound-off-post-or-crossbar"
      ]
    },
    "deliberatePlayCriteriaMet": {
      "description": "SOCCER. Which of IFAB’s five deliberate-play criteria are met. Reported, not scored — there is no pass mark.",
      "type": "array",
      "items": {
        "type": "string",
        "enum": [
          "clear-view",
          "not-quick",
          "expected-direction",
          "coordinated",
          "on-the-ground"
        ]
      }
    },
    "rearSkate": {
      "description": "HOCKEY. The trailing skate in centimetres relative to the LEADING EDGE of the blue line — the edge nearer the attacking zone. Negative is the neutral-zone side; positive means it has broken the plane.",
      "type": "number"
    },
    "skateOnIce": {
      "description": "HOCKEY. Since 2021 this does NOT affect a zone entry — a skate above the plane is onside. It is decisive when tagging up, where the skate must contact the line.",
      "type": "boolean"
    },
    "situation": {
      "description": "HOCKEY. zone-entry (default), or tag-up for clearing a delayed offside. The same skate position can give opposite answers.",
      "type": "string",
      "enum": [
        "zone-entry",
        "tag-up"
      ]
    },
    "stick": {
      "description": "HOCKEY. Ignored, and reported as ignored. Skates decide it.",
      "type": "number"
    }
  },
  "required": [
    "sport"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}

Return the structural differences between soccer offside and hockey offside, dimension by dimension. Use this when someone asks how the two compare, or when you are about to reason about one sport using an intuition from the other — which is the commonest way to get either wrong. They differ on what part of the player is measured, when the picture freezes, whether position alone is an offence, what happens at exactly level, what resets the situation, and which restarts are exempt. Takes no arguments. Returns the comparison table.

{
  "type": "object",
  "properties": {},
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}