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定義技能

技能(ability) 是一個JavaScript函數，當單位具有作為唯一參數的技能，這函數能接收它並傳回一個JavaScript物件：

function walk(unit) {
  return {
    // Ability definition.
  };
}

步行技能 (walk) 是一個行動，先讓我們指出這個特性：

function walk(unit) {
  return {
    action: true,
  };
}

然後我們需要寫上這個技能的描述，所以玩家能夠知道它的功能：

function walk(unit) {
  return {
    action: true,
    description: 'Move one space in the given direction (forward by default).',
  };
}

來到最後但同樣重要的步驟，我們需要在perform函數寫上這技能的邏輯推理， Here, we can use any of the methods in the Unit Maker API. 開始吧：

function walk(unit) {
  return {
    action: true,
    description: 'Move one space in the given direction (forward by default).',
    perform(direction = 'forward') {
      const space = unit.getSpaceAt(direction);
      if (space.isEmpty()) {
        unit.move(direction);
        unit.log(`walks ${direction}`);
      } else {
        unit.log(`walks ${direction} and bumps into ${space}`);
      }
    },
  };
}

技能會被添加到abilities物件中的一個鍵下， 讓我們將步行技能(walk ability)添加到勇士的walk鍵下 (因為我們希望勇士呼叫warrior.walk()時，就能使用這個技能)：

const Level1 = {
  description:
    "You've entered the ancient castle of Eastwatch to escape from a blizzard. But it's deadly cold inside too.",
  tip:
    "Call `warrior.walk()` to walk forward in the Player's `playTurn` method.",
  timeBonus: 15,
  aceScore: 10,
  floor: {
    size: {
      width: 8,
      height: 1,
    },
    stairs: {
      x: 7,
      y: 0,
    },
    warrior: {
      character: '@',
      maxHealth: 20,
      position: {
        x: 0,
        y: 0,
        facing: 'east',
      },
      abilities: {
        walk: walk,
      },
    },
  },
};

在第二層，我們需要再添加兩個技能：攻擊(attack) 及感應(feel)。

首先，讓我們定義攻擊技能：

function valyrianSteelSwordAttack(unit) {
  return {
    action: true,
    description:
      'Attack a unit in the given direction (forward by default) with your Valyrian steel sword, dealing 5 HP of damage.',
    perform(direction = 'forward') {
      const receiver = unit.getSpaceAt(direction).getUnit();
      if (receiver) {
        unit.log(`attacks ${direction} and hits ${receiver}`);
        unit.damage(receiver, 5);
      } else {
        unit.log(`attacks ${direction} and hits nothing`);
      }
    },
  };
}

然後，讓我們定義感應技能，與攻擊相反的是，感應是一個感官技(sense)，所以我們可以略去action鍵：

function feel(unit) {
  return {
    description:
      'Return the adjacent space in the given direction (forward by default).',
    perform(direction = 'forward') {
      return unit.getSensedSpaceAt(direction);
    },
  };
}

注意：在感官技傳回一個或多個空格時，請使用 unit.getSensedSpaceAt()，而非unit.getSpaceAt()。 The former returns a space that exposes only the Space Player API, whereas the latter exposes the Space Maker API and is meant to be used internally, like in the attack ability before.

最後，讓我們添加這些技能給第二層的勇士：

const Level2 = {
  description:
    'The cold became more intense. In the distance, you see a pair of deep and blue eyes, a blue that burns like ice.',
  tip:
    "Use `warrior.feel().isEmpty()` to see if there's anything in front of you, and `warrior.attack()` to fight it. Remember, you can only do one action per turn.",
  clue:
    'Add an if/else condition using `warrior.feel().isEmpty()` to decide whether to attack or walk.',
  timeBonus: 20,
  aceScore: 26,
  floor: {
    size: {
      width: 8,
      height: 1,
    },
    stairs: {
      x: 7,
      y: 0,
    },
    warrior: {
      character: '@',
      maxHealth: 20,
      position: {
        x: 0,
        y: 0,
        facing: 'east',
      },
      abilities: {
        attack: valyrianSteelSwordAttack,
        feel: feel,
      },
    },
  },
};

我們不需要加添加步行技能給第二層的勇士，因為他已經在第一層學會了這技能。

非常好！但勇士仍未有機會揮動他的瓦雷利亞鋼劍，就讓我們添加一名敵人給他戰鬥吧！