Programming Project 1.09 Pokemon´ Battles Solved

The most important part of this update is to add the Pokemon´ battle minigame.

If you are not familiar with Pokemon´ battles (or if you are), here’s a YouTube video of an example battle: https://www.youtube.com/watch?v=Jpdy9pZyGH4. Please don’t ask me why this video has over 2.3 million views1. I don’t know. Perhaps there are a lot of professors out there having their students write Pokemon´-inspired games?

Pokemon´ battles are characterized by a turn-based interaction between two trainers or between a trainer (the PC) and a wild Pokemon´ (the ones which appear in the tall grass). Battles with a wild Pokemon´ end with the capture of the wild Pokemon,´ with either the wild Pokemon´ or the trainer fleeing the battle, or with either the wild Pokemon´ or all of the trainer’s Pokemon´ getting knocked out. Trainer battles end when all of one trainer’s Pokemon´ are knocked out. Trainer battles cannot be fled, and pokemon´ are not available for capture in trainer battles.

A Pokemon´ is knocked out when it’s hitpoints fall to zero. A knocked out Pokemon´ is unavailable for battle until it is revived.
As with other areas of our game, we’ll be simplifying Pokemon´ game mechanics in implementing bat-tling. The most important simplifications we’ll make are that we won’t be implementing status effects (there are simply too many of them to make it a reasonable assignment; but, of course, you’re welcome to do it if you want to) and we won’t implement Pokemon´ abilities (for the same reason).

Each party takes turns in a Pokemon´ battle, with each taking an action each turn. If a trainer’s chosen action is anything other than a Pokemon´ move, this receives maximum priority. If both moves in a turn are Pokemon´ moves, then the Pokemon´ whose move has the higher priority (moves.priority) goes first; if both moves have the same priority, then the Pokemon´ with the highest speed (level adjusted) goes first, and if that is also equal, then choose one at random.. If a Pokemon´ is knocked out or captured before using its move, its turn is forfeit.

Pokemon´ moves can miss. The chance of a Pokemon´ evading a move is modified by status effects, which we ignore. This simplifies accuracy to be a simple percentage given by moves.accuracy. If rand() mod 100 < moves.accuracy, the move hits; otherwise it misses. Once a move hits, damage is given by the following formula:


2

Level
+ 2

P ower

Attack


!  Critical  random  ST AB  T ype















5


50
Defense
+ 2












where Level is the level of the attacking Pokemon,´ P ower is the power of the move (moves.power); Attack is the attacking Pokemon’s´ level-adjusted attack stat; Defense is the defending Pokemon’s´ level-adjusted defense stat2; Critical is 1.5 if the attack is a critical hit, otherwise 1; random is a uniformly distributed random number in [85; 100]; ST AB is the same type attack bonus of 1.5 if the move’s type matches the attacking Pokemon’s´ type, else 1; and T ype is the type effectiveness modifier of 0, .25, .5, 1, 2, or 4, depending on both the move type and the target Pokemon’s´ type (you may use 1 here to simplify


1Now 2.5 million views (S2023), 2.7 million (F2023). Want to make bank on YouTube? Post boring af Pokemon´ videos and monitize that shi-stuff!

    • Pokemon´ differentiates between attack and special attack (similarly for defense) and physical versus special moves. If you know nothing about this, ignore this footnote; otherwise, we’re not going to honor these mechanics, so you may handle it however you like. The most straightforward solution is to simply ignore special attack and special defense.

this mechanic). The move’s damage is decremented from the defending Pokemon’s´ HP, and the defender is knocked out if its HP reaches zero.
In order to calculate STAB, you’ll need the attacking Pokemon’s´ type. This is given in

pokemon types.type id. You’ll find that many pokemon´ have two types (are dual typed). A move gets STAB if any of a Pokemon’s´ types matches the move’s type.

An attack earns a critical hit if it hits and a random number in the range [0; 255] is less than a threshold
value given by bBaseSpeed c (floor is just integer division!) where BaseSpeed is the base value (not level-
2
adjusted) of the attacking Pokemon’s´ speed stat.

During battle, the PC has the following options, which should all be implemented in the battle place-holder(s) that were added last week:

    1. Fight - The active Pokemon´ uses one of its moves; player chooses the move if PC, otherwise the AI chooses (see below).

    2. Bag - Use an item from the trainer’s inventory. We will implement revives, potions, and Pokeballs´ (more below)

    3. Run - Attempt to flee the battle

    4. Pokemon´ - Switch to a different active Pokemon´. A trainer may have up to 6 active Pokemon´.

The fight mechanic is described above.

The bag mechanic consumes an item from the trainer’s inventory. The trainer must be carrying the item in order to use it. A revive will revive a knocked-out Pokemon´ and restore it to half its max HP. A potion will restore up to 20 HP, never taking the Pokemon´ above its max HP value. Pokeballs´ may only be used in battles with wild Pokemon´ and will attempt to capture them.
The PC may only run from wild Pokemon´ (battles with trainers must go until all of one trainer’s Pokemon´ are knocked out). Attempts to run may fail. You may simplify the flee mechanic by simply hard-coding a fixed probability of fleeing.3

Only one Pokemon´ may be active in a battle at any time. Switching Pokemon´ will change the active Pokemon´. A Pokemon´ may only be switched in if it is not knocked out. A trainer may carry up to 6 Pokemon´ at a time. The first Pokemon´ (e.g., in the array) always starts the Pokemon´ battle, and switching Pokemon´ uses the turn.

Start the PC with a small number of potions, revives, and Pokeballs´. These items are usable in battle

(Pokeballs´ are only available in battles with wild Pokemon)´. Detailed catch mechanics can be implemented in 1.10, if you desire. For now, if the PC has fewer than 6 Pokemon,´ every attempt to catch succeeds, but if the PC has 6 Pokemon,´ every attempt to catch will cause the wild Pokemon´ to escape from the Pokeball´ and flee.
The NPC side of Pokemon´ battles needs to be “AI” driven. I put this in quotes because you may make your AI as simple or as complicated as you like. It would be sufficient to choose a random move from the first Pokemon,´ switching Pokemon´ only when the current Pokemon´ is knocked out.


    • If you’re interested, the full escape probability is calculated by

    • %
OddsEscape =
SpeedT rainer   32
+ 30

Attempts

b
SpeedW ild
cmod256





4





where SpeedT rainer is the level-adjusted speed to the trainer’s active Pokemon;´ SpeedW ild is the level-adjusted speed to the wild Pokemon;´ and Attempts is the number of times the trainer has attempted to escape this battle (including the current attempt). OddsEscape is out of 256, thus if rand() mod 256 < OddsEscape, the trainer escapes.

Pokemon´ are not restored to full health automatically after battle. Visiting a Pokemon´ Center should restore and fully heal all of the PC’s pokemon´. Visiting a PokeMart´ should restore the PC’s supplies (im-plement a shopping mechanic if you would like, but all you need to do is restore the PC’s supplies to the default numbers they started with). Implement the ’B’ command that will allow the PC to access the bag outside of battle and apply restores and heals to party pokemon´.