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.

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!