Pokebot — Amanda Patricks

Pokebot’s Versus tab: Gyarados looked up as the opponent, with Electric ×4 and Rock ×2 as the types to hit it with, and a saved team ranked from “Send it out” (Pikachu) to “Keep it benched” (Charizard)

Pokebot’s Versus tab rating a saved team against Gyarados. Data from PokéAPI. Pokémon is © Nintendo / Game Freak; this is an unofficial fan project.

Where it started

Over four years ago I took Harvard’s CS50 on edX, and my capstone was Pokebot: a Discord bot that helped you choose the right Pokémon and berries based on what you already had.

It was written in Python. You typed commands in chat, like !versus gyarados, !addmon pikachu or !flavor sweet. The bot called PokéAPI for the data and saved each player’s Pokémon and berries in a small SQLite database, keyed by their Discord user. Ask it about an opponent and it suggested types to use and which of your saved Pokémon to try.

Rebuilding it for the web

A Discord bot needs a server running around the clock and a database to host. For a portfolio piece I wanted something anyone could open in a browser. So I rebuilt it as a static React + TypeScript app on Cloudflare Pages:

The browser calls PokéAPI directly, so there’s no server and no database to run
Your team and berries (“pockets”) are saved in the browser instead of SQLite, with backup and restore to a JSON file
Name fields autocomplete from PokéAPI’s full Pokémon and berry lists
Three tabs carry over the bot’s commands: Versus, Berries (browse by flavor or look one up), and My pockets

Getting the matchups right

The original bot built its advice by combining lists of “takes double damage from” for each of the opponent’s types. That works for single-type Pokémon, but it breaks down for dual types. Against Gyarados (Water/Flying), it recommended Ice, which is strong against Flying but weak against Water, so it actually lands at ×1. And it couldn’t tell you that Electric hits ×4.

The new version uses the full type chart and multiplies across both of the opponent’s types, so it handles ×4 weaknesses, ×¼ resistances and ×0 immunities correctly. For any opponent it shows:

Hit it with: every type that deals more than ×1, with its exact multiplier
Don’t bother with: types it resists or is immune to
Its attacks are strong against: the types its own attacks hit super-effectively

Rating your team

The part I most wanted from the start: which of my Pokémon should I send out? Each saved Pokémon is rated two ways: how hard it hits the opponent, and how hard the opponent hits back. It then gets one of four verdicts:

Send it out: hits for ×2 or more and isn’t weak to the opponent
Hits hard, but weak to it: a gamble that trades blows
Even match: no edge either way
Keep it benched: the opponent has the advantage

The team is sorted best pick first, so the answer is at the top.

Being a good API citizen

PokéAPI is free and community-run, and it asks apps to cache what they fetch. Pokebot keeps only the fields it needs from each response and caches them both in memory and in the browser. Looking up the same Pokémon twice never hits the network again.

Tested

The type math has unit tests built on real matchups: Pikachu vs. Gyarados should be ×4 and “Send it out”, Ground vs. Gyarados should be ×0, Golem should beat Charizard, and a mixed team should sort in the right order. If I change the logic, the tests tell me right away whether a recommendation broke.