/// Our hero!struct Hero has key, store {  id: UID,  /// Hit points. If they go to zero, the hero can't do anything  hp: u64,  /// Experience of the hero. Begins at zero  experience: u64,  /// The hero's minimal inventory  sword: Option<Sword>,  /// An ID of the game user is playing  game_id: ID,}

/// The hero's trusty swordstruct Sword has key, store {  id: UID,  /// Constant set at creation. Acts as a multiplier on sword's strength.  /// Swords with high magic are rarer (because they cost more).  magic: u64,  /// Sword grows in strength as we use it  strength: u64,  /// An ID of the game  game_id: ID,}

/// A creature that the hero can slay to level upstruct Boar has key {  id: UID,  /// Hit points before the boar is slain  hp: u64,  /// Strength of this particular boar  strength: u64,  /// An ID of the game  game_id: ID,}

/// Slay the `boar` with the `hero`'s sword, get experience./// Aborts if the hero has 0 HP or is not strong enough to slay the boarpublic entry fun slay(  game: &GameInfo, hero: &mut Hero, boar: Boar, ctx: &TxContext) {  check_id(game, hero.game_id);  check_id(game, boar.game_id);  let Boar { id: boar_id, strength: boar_strength, hp, game_id: _ } = boar;  let hero_strength = hero_strength(hero);  let boar_hp = hp;  let hero_hp = hero.hp;  // attack the boar with the sword until its HP goes to zero  while (boar_hp > hero_strength) {    // first, the hero attacks    boar_hp = boar_hp - hero_strength;    // then, the boar gets a turn to attack. if the boar would kill    // the hero, abort--we can't let the boar win!    assert!(hero_hp >= boar_strength , EBOAR_WON);    hero_hp = hero_hp - boar_strength;  };  // hero takes their licks  hero.hp = hero_hp;  // hero gains experience proportional to the boar, sword grows in  // strength by one (if hero is using a sword)  hero.experience = hero.experience + hp;  if (option::is_some(&hero.sword)) {    level_up_sword(option::borrow_mut(&mut hero.sword), 1)  };  // let the world know about the hero's triumph by emitting an event!  event::emit(BoarSlainEvent {    slayer_address: tx_context::sender(ctx),    hero: object::uid_to_inner(&hero.id),    boar: object::uid_to_inner(&boar_id),    game_id: id(game)  });  object::delete(boar_id);}