u/mathalon

I'm building a competitive math site - think chess.com, but for math problems. Every problem has its own rating, and so do you. We run Glicko-2: everyone starts at 1500, rating deviation 350.

Today's design question: what should happen to your rating when you stop playing for a month?

Glicko-2 already inflates your rating deviation over time, so returning players get bigger swings until the system re-learns their level. But should the displayed number decay too? Chess.com doesn't decay ratings; plenty of ladders do.

For decay: the leaderboard stays alive, and comebacks feel earned.

Against: punishing someone for taking a vacation feels bad, and RD inflation already models the uncertainty.

What would you actually want as a player?

Site if you're curious: mathalon.app

Today's daily problem: ten people attend a party, no three guests have all shaken hands with one another, and you want the largest possible number of handshakes.

I'm building a site where every problem carries its own rating, the same way players do, and this one landed at 1900. In our pool that roughly means "most people who attempt it get it wrong on the first try". I'd like a sanity check on whether that number feels honest, because the statement is one line and the key idea is short once you see it. What makes it hard is that the wrong answer is very attractive.

The part I'm still not happy with is cold start. A brand-new problem has no solve data at all, so the initial rating is an estimate from an LLM pass over the text, and it only drifts toward the truth once enough people have attempted it. Early on that means the first few solvers get rating changes based on a number that is probably wrong, and I don't love that.

Things I've considered: widening the problem's rating deviation so early attempts move it faster but move the player less, holding rating changes in escrow until a problem has N attempts, or simply not awarding rating on problems below some confidence threshold. Each has an obvious downside.

If you've built anything with two-sided ratings — players and items both rated — I'd be curious how you handled the first hundred interactions.

Problem's up at mathalon.app/daily if you want to try it.

We built a competitive math platform where both problems and solvers carry Glicko-2 ratings. A new problem drops every day, you can race the clock in Rush, or go head-to-head in ranked 1v1. Practice mode adapts to your level.

Free to play: https://mathalon.app — happy to answer questions about how the rating system works!