Duelist Kingdom

Yu‑Gi‑Oh! GOAT Format (April 2005) in your browser: a roguelike, Bo3 tournaments with side decking, and rooms to play your friends. Free, no install, no account.

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PC and phone (landscape) · English and Spanish

Build 1.0

Trailer

Game modes

Duelist Kingdom

A roguelike run across the island: Star Chips, a branching map, packs, encounters and Pegasus at the castle.

Free Duel · Bo1

20 premade meta decks ready to play, or your own, against four bot difficulties.

Swiss Tournament · Bo3

32 players, 5 Swiss rounds and a top 16 cut, with side decking between games.

Play with a friend

Your own decks, Bo1 or Bo3 with side decking, each player from their own browser.

Why it exists

To be a fun and challenging single-player game for new players and especially for experienced ones, and a way to play GOAT meta decks against a machine or against friends with everything automated: train for locals or tournament brackets without the manual interaction of Dueling Book.

The rules aren't hand-written. It runs ocgcore, the engine EDOPro uses, compiled to WebAssembly and started in GOAT mode, with 2005 priority for cards like Black Luster Soldier, Chaos Sorcerer, Tribe-Infecting Virus and Breaker.

A GOAT Format duel: board, phase strip and card detail panel — The duel board. Drag from hand to play; hover or tap any card to read it.

A smarter AI

The bot sees only what a player would see, has a plan for each of the 20 meta decks, simulates its options before playing, and is guided by a bank of over 100 meta plays taken from real tournament replays and from misplays players reported. Found a bad play? The Report button in the game sends it straight to the GitHub page with the duel log.

The Swiss tournament: your table, the round's pairings and the side deck button — The Swiss tournament: your Bo3, side deck between games, and every table of the round.

Play with a friend

Create a room and send the code or the link. Browsers connect directly to each other, and the host's browser runs the duel and sends each player only what they're allowed to see. It works from this page and from a downloaded copy, on PC or phone, and you can mix them. Both players need an internet connection and the same version.

A room with two players, deck choice, Bo3 format and time per decision — A room: each player picks a deck, the host picks Bo1 or Bo3 and the time per decision.

Your data

Your decks, runs and tournaments are saved in your own browser, on your own device. Nothing goes to a server. Use Options → Your data → Save backup to keep a copy or move it to another device.

Play offline

Download the zip, unzip it and open goat-simulador.html by double-clicking. Everything travels inside the file except the card artwork, which is loaded from the internet; offline you still play.

Disclaimer

The engine is ocgcore (EDOPro) with some custom adjustments, like establishing priority with Tribe-Infecting Virus, Black Luster Soldier or Breaker. There may still be rulings or plays it doesn't handle: if you see a weird AI play or an interaction that goes against GOAT rulings, please send it with the Report button.
The whole project was vibe coded with the help of Claude. Testing was done mainly by me over several months, plus Claude simulating bot-vs-bot duels.
I don't have an iPhone: everything was tested on PC and Android. If something looks or behaves wrong on iOS, please report it on the GitHub page.