I made a website. It’s called One Million Chessboards. It has one million chessboards on it.

Moving a piece moves it for everyone, instantly. There are no turns. You can move between boards.

What

Well last year I made this game called One Million Checkboxes.

It was a pretty fun time! So I thought I’d do something like this again.

I worked really hard on this one. I hope you like it.

How

This was the most technically challenging thing that I’ve worked on in a long time. I’m going to save a full technical writeup until I see how my decisions pan out, since I think there’s a decent chance I’ll need to make a lot of changes.

But I’ll summarize a few things for you.

• Unlike One Million Checkboxes, I designed this for scale
• The game runs on a single server (!)
• The board is stored fully in-memory; it’s a 2D array of 64 million uint64s
• The backend is written in go. This is my first go project.
• I use a single writer thread, tons of reader threads, and coordinate access to the board with a mutex
• The frontend optimistically applies all moves you make immediately. It then builds up a dependency graph of the moves you’ve made, and backs them out if it receives a conflicting update before the server acks your move.
• The server ships zstd-compressed protobufs to the clients over websockets for state snapshots (approximately a 100x100 square around the client), move and capture updates, and acks/rejections for moves
• Clients are grouped into 50x50 “zones” and only receive moves for zones adjacent to their current zone
• Clients fetch global data (game stats, the minimap, etc) by polling via GET; data is cached in Cloudflare with a low TTL so this is much cheaper than shipping it over every websocket

That last part - optimistic move application with what games people sometimes call “rollback” - is about 1,600 lines of code that took me a ~7 days of fulltime work to write. I don’t remember the last time I wrestled with a problem that hard!

As of 8 PM, 8 hours after launch, players have made about 1.3 million moves and there are about 400 concurrent users most of the time. Load on my server is neglibible!

Can I play

Yes! Play it here.

I really hope you like this one. More updates to come :)