[pyp-w1] RPG Battle System

Today we will be creating a traditional RPG (role-playing game) battle system featuring Mages, Warriors, Dragons, and Skeletons!

We will be breaking the project down into three primary parts: Heroes, Monsters, and Battles.

Heroes represent player characters, they can be one of four classes, Warrior, Mage, Cleric, or Rogue. Depinding on a hero's class they will have different stats and abilities, for example a Warrior is stronger and more durable than a mage and therefore they have a higher strength and constitution. These statistics effect how their various abilities work. As heroes defeat monsters they gain xp (experience points) and if they gain enough experience they level up and become stronger.

Monsters are what the heroes fight. They can be classified into monster families (like dragons and undead) as well as individual monster types within those families (like Red Dragons and Vampires). Monsters have their own abilities depending on a combination of their family and type.

Battles This is what brings everything together. Participants will perform actions in order of their speed attribute - faster units go before slower units. Hero abilities are user determined, monster abilities are used according to their command queue (described below) and target heroes randomly. Battle continues until either all the heroes or all the monsters are wiped out.

Heroes

Features common to all Heroes: When initialising a Hero you may pass a level parameter to specify what level of hero you would like.

• Stats:
• strength
• constitution
• intelligence
• speed
• hp - current hit points
• maxhp - maximum hit points
• mp - current magic points
• maxmp - maximum magic points
• level - current character level
• xp - current experience points
• xp_for_next_level() - when xp == this it causes the hero to level up (should be equal to level * 10)
• gain_xp(xp)- causes the hero to gain xp experience points, should also handle the process of levelling up
• fight(target) - Basic attack dealing damage equal to the hero's strength to the target
• abilities - a collection of strings representing the hero's combat abilities. For example a Mage's abilities would be something like ('fight', 'fireball', 'frostbolt')
• take_damage(damage) - hero takes damage amount of damage, having it subtracted from their current hp
• heal_damage(healing) - hero heals healing hit points, but not beyond their maxhp
• is_dead() - if the hero's hp have been completely depleted this returns True

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Stats Base level stats (strength, constitution, intelligence, speed) for a level 1 Hero start at 6 and may be modified by child classes.

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Hit Points Base level hit points for a level 1 Hero start at 100 + 1/2 of the hero's constitution, dropping any fractions.

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Magic Points Base level magic points for a level 1 Hero start at 50 + 1/2 of the hero's intelligence, dropping any fractions.

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Levelling Up When a hero has xp greater than or equal to xp_for_next_level they level up. Any excess xp is carried over after their xp is set to 0. Upon level up all stats are increased by one (or more if the hero has a stat modifier, this will be explained later). Their maxhp is increased by 1/2 their new constitution and their hp is brought back up to full. maxmp is also increased by 1/2 the new intelligence, mp also being filled. When increasing maxhp or maxmp remember to drop any fractions.

Hero Subclasses

Stat Modifiers Subclasses can apply modifiers to the hero's stats, either increasing or decreasing them. Modifiers should be added directly to the base value of the appropriate stat. At level up if the modifier is positive it is added to to the standard +1 received at level up. Example: If a subclass had a +1 strength modifier it would have 7 strength at level 1 and would gain 2 strength each time it levelled up.

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Special Abilities Each subclass has its own unique special abilities. Many of these abilities have an mp cost, if the hero does not have enough mp to use the ability an InsufficientMP error should be raised. When calculating damage, drop fractions from final damage number.

Warrior

Stat Modifiers

• strength +1
• intelligence -2
• constitution +2
• speed -1

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shield_slam(target)

• Cost: 5 MP
• Damage: 1.5x strength

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reckless_charge(target)

• Cost: 4 HP
• Damage: 2x strength

Mage

Stat Modifiers

• strength -2
• intelligence +3
• constitution -2

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fireball(target)

• Cost: 8 MP
• Damage: 6 + 0.5x intelligence

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frostbolt(target)

• Cost: 3 MP
• Damage: 3 + level

Cleric

Stat Modifiers

• speed -1
• constitution +1

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heal(target)

• Cost: 4 MP
• Heals target for constitution

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smite(target)

• Cost: 7 MP
• Damage: 4 + 0.5x (intelligence + constitution)

Rogue

Stat Modifiers

• speed +2
• strength +1
• intelligence -1
• constitution -2

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backstab(target)

• Cost: None
• Special requirement: Target must be undamaged. If target is damaged must raise InvalidTarget
• Damage: 2x strength

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rapid_strike(target)

• Cost: 5 MP
• Damage: 4 + speed

Monsters

Features common to all monsters: When initialising a Monster you may pass a level parameter to specify what level of monster you would like.

• Stats:
  • strength
  • constitution
  • intelligence
  • speed
• maxhp
• hp
• level
• xp() - returns the xp that would be earned if this monster were to be defeated
• fight(target)
• take_damage(damage)
• heal_damage(healing)
• is_dead()
• attack(target) - Attacks the target using the next ability in the monster's command queue (explained later) Note: Monsters do not use MP

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Stats Monsters start with a base stat level of 8 versus the 6 that heroes receive. Instead of receiving stat modifiers like heroes, monsters may receive stat multiplier instead. These are applied in the following manner: At level 1 a stat is set to 8x the stat multiplier. For levelled monsters set the stat to 8X multiplier + (level - 1)x multiplier, dropping fractions. Monster have a base HP of 10 (this may be overidden by monster families and subtypes, more on this later) to calculate their actual maxhp use the base hp + (level - 1) x (0.5x constitution), dropping fractions as usual.

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XP A monster's xp value may be calculated by taking the average of their stats (strength, constitution, intelligence, speed) and adding it to maxhp % 10.

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Command Queue The command queue determines in which order a Monster uses its abilities. When an ability is used it cycles out to the end of the queue. Example: If a monster had a queue of ['fight', 'bash', 'slash'] the first time it attacked it would use fight, the next time it would use bash and so on.

Monster Families and Subtypes

Monsters are divided into families before being separated into individual monster types. Monster families can have multipliers, abilities, and other special features that apply to all of their members.

Dragons

Family features

• Base HP: 100
• constitution multiplier: 2
• Special feature: Dragons have damage reduction, all damage they take is reduced by 5.
• tail_swipe(target) : Deals strength + speed damage

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RedDragon

• strength multiplier: 2
• intelligence multiplier: 1.5
• fire_breath(target): deals 2.5x intelligence damage

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GreenDragon

• strength multiplier: 1.5
• speed multiplier: 1.5
• poison_breath(target): deals 1.5x (intelligence + constitution) damage

Undead

Family Features

• constitution multiplier: 0.25
• Special feature: Undead take damage from attempts to heal them. Note: The Undead's own special healing abilities do not damage it
• life_drain(target): Damages the target for 1.5x intelligence, healing the Undead for the same amount.

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Vampire

• intelligence multiplier: 2
• Base HP: 30
• bite(target): Deals 0.5x speed damage to the target, healing the Vampire for the same amount. Permanently lowers the target's maxhp by an amount equal to the damage dealt.

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Skeleton

• strength multiplier: 1.25
• speed multiplier: 0.5
• intelligence multiplier: 0.25
• bash(target): deal 2x strength damage

Humanoid

Family Features

• slash(target): deal strength + speed damage

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Troll

• strength multiplier: 1.75
• constitution multiplier: 1.5
• Base HP: 20
• regenerate(*args): Restores constitution health to the Troll.

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Orc

• strength multiplier: 1.75
• Base HP: 16
• blood_rage(target): Deals 2x strength damage to the target while dealing 0.5x constitution damage to the Orc

Battle System

Preparing a battle should be as simple as creating a new Battle while passing in a list of participants. The battle should handle sorting the participants in order of speed and then cycle through the list, moving units to the end of the line as they take turns performing actions.

A Battle should have the following outward facing interface:

• start(): Starts the battle!
• current_attacker(): returns the unit at the front of the initiative queue
• execute_command(command, target): uses an ability on the target

Upon running the start command the program should check to see if the current attacker is a monster, if it is it will pick a hero target at random and use the monster's next attack in its command queue. It will then repeat the process until it reaches a hero's turn. At this point it returns a multi-line string containing all the events that have happened so far and stating what hero's turn it is. (Details on event formatting below.) It is then up to the user to select a target and action and then execute_command. This will run the corresponding command (throwing any appropriate errors, including InvalidCommand if the command doesn't exist) and then resume the cycle of moving through the initiative queue until it reaches a Hero again. At the end of each unit's turn all dead units should be removed from the initiative queue and xp should be rewarded to all heroes for any monsters killed, triggering level ups if appropriate. If at any time all the monsters are wiped out the program should raise a Victory, if all the heroes are killed it should raise a Defeat.

Event formatting Each event should be recorded on a new line in the multi-line string that is returned

• *fight command used: {monster} attacks {target} for {damage}!
• other attack ability used: {monster} hits {target} with {ability} for {damage} damage!
• unit dies: {unit} dies!
• XP is rewarded: {xp} XP rewarded!
• Hero levels up: {hero} is now level {level}!
• Unit ability causes damage to self: {unit} takes {damage} self-inflicted damage!
• Hero's turn: {hero}'s turn!