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Defining Abilities

An ability is a JavaScript function that receives the unit that possesses the ability as the only parameter and returns a JavaScript object:

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

The walk ability is an action, so first of all let's indicate that:

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

Then, we need to write a description for the ability so that the player knows what it does:

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

And last but not least, we need to write the ability's logic in the perform function. Here, we can use any of the methods in the Unit Maker API. Let's do that:

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}`);
      }
    },
  };
}

Abilities are are added to the units under a key in the abilities object. Let's add the walk ability to the Warrior under the walk key (because we want the player to invoke it by calling warrior.walk()):

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,
      },
    },
  },
};

For the second level, we need to add two more abilities: attack and feel.

First, let's define the attack ability:

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`);
      }
    },
  };
}

Secondly, let's define the feel ability. Contrary to attack, feel is a sense, so we can omit the action key:

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

IMPORTANT: When returning one or multiple spaces from senses, use unit.getSensedSpaceAt() instead of 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.

Finally, let's add them to the Warrior of the second level:

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,
      },
    },
  },
};

We don't add the walk ability again in the second level because the Warrior already learned it in the first level.

This is very nice, but the Warrior is not wielding that Valyrian steel sword for nothing. Let's add an enemy he can fight!