xkcd2645
I make stuff - mostly software, sometimes chaos. These are the things I’ve built, shipped, or abandoned with love <3.
A chess engine I've been building since September 2026. Currently in active development.
01 · Search
Principal-variation alpha-beta search with null-move pruning, late-move reductions, singular extensions and five correction histories, tuned by SPSA across 89 parameters.
02 · Evaluation
An efficiently updatable network (NNUE, 768×4 → 512 → 1) trained with bullet on 1.05 billion positions from Leela Chess Zero’s training data.
03 · Testing
Every change plays thousands of games against the previous version in a statistical test (SPRT) on SolsticeBench, a self-hosted OpenBench. Over 220 tests so far, failures included.
04 · Strength
Estimated from 640 games at 60+0.6 against eight engines rated 3529–3745, scoring 59.5%.
A board, a search and a small network trained on a public dataset of positions labelled only with game results.
Generation after generation of networks trained on Solstice’s own self-play games, up to 819 million positions.
A board representation and legal move generator written from scratch, checked against 4.8 billion perft nodes.
Compiled to WebAssembly to play in the browser. First gauntlet: about 3420 CCRL Blitz.
Bigger networks and a long run of search improvements, against stronger opponents.
The first network trained on Leela Chess Zero data gained 41 Elo; the next gauntlet put Solstice at 3687 ± 14.
Languages, by repository
Most-starred repositories
Training a much bigger network with 16 king buckets and 1,024 neurons on 4.7 billion positions, and teaching Solstice to scale well with multithreading.
The goal: the strongest chess engine after Stockfish.
HII! I'm Ethan Pan, aka xkcd2645. I like building things that are useful, weird, or both.
I spend most of my free time either writing code, eating pizza, or sleeping and occasionally get distracted by random interesting math - hence the domain. Euler’s totient function φ(n) counts the integers up to n that are coprime to n. Pretty cool, right? (you're supposed to agree here :)
This site is where I collect the things I've made. Some are serious projects, some are quirky experiments, but all of them were really fun to build. After all, it's the friends we made along the way amirite? :-)
Here's a bit more about me and how I learned coding.
Dabbled with HTML, playing with divs, spans, tables and throwing H1s all around the page.
Learnt python, tried creating a chess-playing program which kinda worked. Engine uses a simple evaluation with piece values and piece square tables as well as an alpha-beta minimax search.
Learnt C# and participated in a chess coding competition. Engine has several optimisations including pruning techniques like NMP, RFP, FP and uses advanced move ordering.
Learnt C++ and built a superhuman chess engine with the help of a community. Engine is heavily optimised and tested with SPRT. Engine values are tuned with SPSA. Further developments in engine evaluation with the help of a texel tuner.
EONS ago, back in Primary 4, my dad bought me a "mini laptop", which was a Chromebook, and taught me how to code in HTML, CSS and JS to create my very own websites. That's when I started fumbling around with frontend development, creating a few interesting mini sites including a poetry site, a chess website and a super simple animal encyclopedia that could make animals noises. Sadly, many of these sources were lost after my Chromebook spoiled.
After I finally got a proper laptop, I also started learning a new programming language - python. Mostly with the help of ChatGPT back in Primary 6, I taught myself the basic syntax of python and how to write my first fully functional chess-playing program with the minimax algorithm. This chess program wasn't any good though, and I considered it quite a failure, but the fun was undeniable.
After my PSLE, I was accepted into my dream school then, BPGHS. I was elated. Between year 1 and 2, having become quite fluent in python, I decided to challenge myself to learn C# and participate in a chess coding and token optimisation competition hosted by the one and only Sebastian Lague on Youtube. However, it turned out I was too ambitious and could not finish the project in time before the deadline. Sad, but I was grateful to be able to learn C# while I'm at it.
When year 3 arrived, I decided it was time to learn C++, a language that is arguably one of the most fundamental and impactful in software development, but I learnt it cuz I heard it was quite fast. Guess how I decided to approach learning the language? Yes- by creating another chess engine. This time, I had to make it count and successfully created Weak, a Superhuman chess engine, with the help of fellow members in the Stockfish Discord server.
Chess is life, basically. When there are no exams, I frequently go to local chess clubs - eg. Queenstown Chess Club on Sundays - to play a few games. Started loving chess ever since Primary 3 when my school introduced a board game programme.
Ever since I got my first DSLR in Sec 3, I've been completely engrossed in taking amazing pictures. A few Youtube videos later, I learnt about composition, lighting and editing techniques the make a picture pop! I find intentional photography has quite the power to keep memories alive.
After my mum first gave me her mini ukulele, I played it whenever I felt sad or emotionally not ok because it has a way of calming me. Now I play it mostly out of enjoyment. I sometimes do fingerstyle on the uke to create melodies but I'm in no way an expert.
Joined the Astronomy club of BP in Sec 3 for one reason - to learn more about the Cosmos! The experience was one-of-a-kind and exposed me to very interesting topics that I've never come across in school, ever. I'm also a proud PISCES.
Yes, I like hacking stuff, ethically. I enjoy doing CTF challenges in HackTheBox and am currently studying network security and penetration testing.
I've a mini home chemistry lab with all the standard school apparatus as well as additional apparatus to do cool experiments. Some of my favourites are the different coloured flames, iodine-clock reaction and the chameleon reaction.
I've joined the Singapore Math Olympiad ever since Sec 2. I was not particularly good at those though, only obtaining a Bronze at both junior and senior level. In Sec 3 I joined the SJPO and also got a Bronze, which I was really proud of. In 2026, I joined the International Mathematical Modelling Challenge (IMMC) and wrote about a 50-page report on using mathematics to solve real world challenges.
Will always love camping as a Scout. As they say once a scout always a scout! I enjoy outdoor activities when I'm not coding and I hope to "touch grass" more often.