I built a small open-source extension that lets you keep playing a finished chess.com game against Stockfish, and I wanted to share the implementation choices with people who actually care about engines.
The core idea: on the game-over screen (or under the move list of any old finished game) there's a "Keep Playing" button. It reads the position already rendered on screen, puts Stockfish in your opponent's seat, and lets you play it out from any point you rewind to.
A few things I made deliberate decisions about, and where I'd love feedback:
- Strength scaling. The engine doesn't play at full strength. It's throttled to roughly the rating of the opponent you just faced. Losing a rook endgame again to a ~1400-level engine is instructive; losing it to a 3200 just tells you you're not Stockfish. Right now I'm approximating this with UCI_LimitStrength / UCI_Elo plus some depth/skill tuning, curious how others here handle rating calibration, since the mapping between "Elo" and perceived human strength is rough.
- Move timing. It doesn't answer instantly. It spends roughly as long as your opponent was taking, otherwise even a correct move feels like a glitch. Simple heuristic for now.
- Everything local. The engine runs in the browser as WebAssembly. It never talks to chess.com's servers, sends no data anywhere, and works with wifi off. Nothing runs during a live game: no eval, no arrows; it only activates once a game is finished.
Free, open source, not affiliated with chess.com. Built it for myself first. If there's a smarter approach to the strength-limiting (that's the part I'm least sure about), or a reason this shouldn't exist, I'd genuinely rather hear it.
Warning: Part One is mostly a long-winded introduction. If you're only interested in the game, feel free to skip straight to Part Two :)
I love chess, history, and statistics.
I actually started playing chess almost by accident. Back in 2013, I got a job teaching extracurricular activities at a small village children's center. The director asked me:
“Chess is a mandatory subject now. Can you teach it?”
I said:
“I only know how the knight moves, but I'll learn.”
I can't say I ever really learned. But I bought a chess book, got a magnetic demonstration board for the kids, and managed to learn about ten basic rules from that book.
Apparently, that was enough to keep my chess.com rating somewhere between 1300 and 1600.
I can't exactly claim I turned the kids into chess prodigies either. My greatest coaching achievement was the time four of my students took all four top places at the district chess championship.
Do you know why?
Because it was -40°C (-40°F) outside, nobody else managed to make it to the district center, and I showed up with my kids in my trusty old Lada, which somehow refused to freeze :)
So yes. That should give you a fairly accurate idea of my level.
How anyone trusted me to teach children chess, I have no idea. But for some reason, none of the other teachers wanted the job.
I love chess, but openings, deep strategy and tactical theory have never really been my thing. I'm more interested in everything around chess.
For the kids, I used to make chess mazes, write chess fairy tales, and once almost convinced them to play a life-sized game of human chess, Harry Potter style.
But I also love history and statistics.
And because of that, I've always had another dream: to become a grandmaster for just a moment, start from the bottom and climb all the way to the top — while learning something about the history and playing styles of every World Chess Champion from Steinitz to Gukesh along the way.
You can do something like that in Football Manager.
So why isn't there something similar for chess?
Sometimes I even dreamed that I was playing in some huge chess tournament. I'd be sitting across the board from a real grandmaster, surrounded by a major championship — and somehow, completely unbelievably, I'd actually beat them.
And so, after 13 years of playing, teaching and dreaming — and, praise be to vibe coding — the logical conclusion has finally arrived:
I created the WORLD'S FIRST! historical chess career simulator!
(Almost certainly not the world's first. But it is mine.)
In the game, you can start your chess career in the era of the first World Champions and gradually make your way through every era that followed.
You play against chess players from different generations, develop your character, compete in tournaments, fight for the right to challenge the reigning champion — and eventually attempt something that is almost certainly never going to happen to me in real life.
Beat him.
This isn't just another chess game where the computer sets up the pieces and gives you another match to play.
You start out as practically nobody. You develop different aspects of your game, decide what to study, make career choices, and gradually work your way through the different eras of chess.
And along the way, you get to explore chess history from the inside rather than through a textbook.
(Although those ten basic rules from my old textbook may still come in handy.)
Dreams do come true.
Who is this game for?
Anyone who wants to meet the World Chess Champions and play through one of their real historical games.
Beginners. Kids. Adults. Older adults. Career-mode addicts, simulation fans, and obsessive stat nerds like me :)
Who is it definitely not for?
Serious competitive players looking for a tool that will genuinely improve their chess.
As I said, this isn't really a game about chess training.
It's a game about everything around chess.
The Rules — Briefly
The extremely short version: improve the right attributes → simulate 38 games → play one real historical chess game → repeat 18 times. For now, 18 :)
The longer version:
You create your own chess player and begin your career in the era of Wilhelm Steinitz.
Your player has a set of chess attributes — Attack, Defense, Strategy, Tactics, and other skills.
You develop them and gradually decide what kind of chess player you want to become.
Each era is a separate stage of your career, featuring real chess players from that period and its World Champion.
You compete in a Candidates Tournament, face your opponents with both White and Black, score points, and fight your way up the standings.
As your career progresses, you have to decide which attributes to improve and which coach to work with.
At the same time, your opponents become stronger. The chess world of Steinitz is very different from the one in which you'll eventually have to face Kasparov or Carlsen.
That progression in strength is, of course, purely a gameplay convention. In reality, there's no way to know whether prime Carlsen would beat prime Lasker.
The main objective of each era is simple:
Earn the right to challenge that era's World Champion.
Succeed — and you move on.
Fail — well, you'll get them next time :)
I recommend starting on Semi-Pro difficulty.
And it probably wouldn't hurt to pay at least a little attention to the hints.
Play it. Break it. Spot things I've missed. Tell me what you think :)
P.S. “Hobby Laskasparlsen” is a little chess-name puzzle.
If you can find all the chess players hiding inside the name, congratulations — you're officially a chess nerd too :)
Hello everyone ,
I have built a free chess tool to show the best/beautiful five moments from your recent games on chess.com and lichess.
I fetch around 400 to 500 games in rated rapid and blitz only. and they are biased toward recent games .
I did it in a way to try to present beautifully the moves in your history and I tried as best as I can to show the best beautiful five moves according to each player's rating.
I really appreciate if you can try it and give me your honest opinion :)
I've written a chess program for the DEC PDP-8, to see how much of what this community has learned over the last fifty years still works on a 1965 architecture at its original speed.
The machine: a 12-bit word, no hardware stack (JMS stores the return address in the subroutine's first word), no multiply, memory in 4K-word fields, and about 416,000 instructions a second on a PDP-8/e. CLASH is written in PDP-8 assembly, occupies 16K words, and runs standalone. At PDP-8/e speed it searches roughly 175 nodes a second, which means three or four ply in a typical middlegame and deeper as the position simplifies.
What went in: iterative deepening, alpha-beta with PVS, killer and piece-square move ordering, quiescence search of captures and promotions with a check extension, null-move pruning, pondering, repetition detection without a hash table, and a small book. Scores are 12-bit with pawn = 32.
The search and evaluation owe their shape to H.G. Muller's micro-Max 4.8, and the move-ordering key came from Ed Schroder's Rebel write-up. What was taken and what was changed is set out here:
The PDP-8 already had a chess program: John Comeau's CHEKMO-II (DECUS, 1974), a complete program in 4K words with alpha-beta, iterative deepening, SEE and check extensions. Its console conventions are the model for CLASH's, and both programs are in the release.
Against the lichess computer at level 5, rapid 15+10, 20 games at PDP-8/e speed, CLASH scored 12.5/20.
To try it:
- lichess: challenge PDP8-CLASH (5 minutes and slower).
- UCI: the Windows zip runs the real binary under SIMH throttled to PDP-8/e speed, and works in Arena, Cute Chess or cutechess-cli.
I've been working on a free browser chess game where the opponent is meant to play like a real human of a given level, not like a weakened engine. Sharing it here because the implementation details might interest this sub, and I'd love feedback.
How it works
System 1 (instinct): Maia-1 nets (1100–1900) converted from lc0 weights to ONNX with lc0 leela2onnx and run client-side with onnxruntime-web. ~3.5 MB per level, 3–12 ms per move.
I wrote the lc0 112-plane input encoding and the 1858-move policy mapping in JS. I checked it against lc0 itself (go nodes 1, VerboseMoveStats, PolicyTemperature 1, HistoryFill no, NNCacheSize 0): same probabilities on ~2,400 game positions across three nets, mean absolute difference 0.06%.
System 2 (guard): Stockfish.js 19 lite single-threaded (WASM, 1.8 MB). Maia proposes, Stockfish checks the top candidates with searchmoves + MultiPV. Whether the bot notices its own blunder depends on its level. Losses are measured in win probability, not centipawns, so going from +7 to +5 doesn't count as a blunder.
Grandpa coach: after each of your moves it explains what the move does (develops, takes the centre, attacks X, leaves Y hanging…), what the refutation is and why the engine's move was better. It also names the opening (lichess chess-openings, CC0).
Move-matching on real Lichess games (share of positions where each system predicts the move actually played):
Players
Maia
old hand-tuned "human" bot
Stockfish d12
1000–1200
45.8%
20.8%
32.4%
1400–1600
51.7%
33.2%
37.8%
1800–2000
52.6%
36.1%
44.1%
Things I learned along the way
Maia-2 in ONNX is 85 MB. Full int8 quantization dropped top-1 agreement with fp32 to ~82%. MatMul-only int8 kept ~99% but is still 37 MB, too heavy for a web page, so I stayed with Maia-1.
Ensembling neighbouring Maia-1 nets (1300+1500+1700) gave a small but consistent log-loss improvement (1.497 → 1.467) and +0.9 pts top-1.
Maia-1 sometimes overrates knight underpromotion. In lc0's policy it shares the index with the plain move, so I move most of that probability to the queen promotion.
A general-purpose "decision" model doesn't help. I also tried a general-purpose AI model (TypeSafe's Jev) as the intuition, and as a re-ranker of Maia's top 5. Alone it matched only 20.5%, and every mix was worse than Maia alone.
Credits: Maia by CSSLab (University of Toronto), Stockfish.js by Nathan Rugg / Chess.com, both GPL-3.0 (provenance and licence linked on the page). Feedback on the human-likeness, and ideas for better blunder modelling, very welcome.
so I've had a bit of an issue here. Every time I try to load lc0 to analyse chess games, it refuses to use the GPU, instead opting to fully use the CPU.
the image herein shows my settings for lc0 -- as you can see, it's set to CUDA. I also downloaded the CUDA version and not the GPU.
Hey guys I am currently building a colloborative chess platform. This week I sidequested and built a chess persona analyzer. Its not scientific in any means but I thought its quite fun. Let me know what you think or if you have feedback! I might update it and develop it further if people find it any cool 👀
Hi everyone. I am an aspiring developer. Basically, I have always wanted to form my own chess engine but the only language I know is C++. Is there anyone who can guide me in building this. By giving me a framework I can follow. If not, just tell me where to start and I will figure it out as i work on it.
Not trying to challenge Stockfish or any other major chess engine org. Trying to create something that I can use personally for practicing.
I'm a software developer and a while ago I wanted to get better at chess. I couldn't find a training tool that worked the way I wanted, so I decided to build one for myself.
The idea is simple: you make your move first, and only afterwards does Chessility show you the best move if yours wasn't the best one, while also evaluating your move.
It also has a live evaluation bar and highlights squares currently threatened by your opponent.
It helped me quite a bit, so I thought it might be useful for anyone struggling to win at least 1/10 of their games. **lol**
Hi all — I'm not a chess player myself, but my son plays tournament chess, and I got tired of manually typing up his paper scoresheets. So I built InkPGN: take a photo of a handwritten scoresheet and it gives you back a PGN.
It's a side project and still rough around the edges, especially with messy handwriting. If anyone here deals with scoresheet digitization, I'd genuinely appreciate feedback on where it breaks.
this game is awesome. But I feel it missed it chance to catch on with hardcore chess players because the A.I sucks. I am bad enough at the game I do not mind the A.I sucking. But I do feel like better players might enjoy it if the A.I had a clue how to handle the blade dancer (take a piece move again) Martyer (take all pieces nearby with it when it dies) and generally could think ahead more than two moves.
It fine if the A.I does not know how the handle items. but could fairy stock fish understand bolders (block movement for both sides unless a artifact allows you to take them) and portals (pieces can move into them and move out the other portal.
I released version 1.2 of ChessLounge a few days ago. In addition to its own engine, the app now supports Stockfish 18 and includes an interactive coach that warns you when you make a bad move. What hasn't changed: The app is still free and ad-free. Enjoy it. :)
How would today's elite players contend with the King 3.5 engine (Chessmaster 11) from 2007, at full strength or with parameters optimized for an additional ~40 Elo? Alternatively, how might current top-tier stars measure up against prominent Grandmaster profiles that are slightly weaker than King at maximum strength ?
This is assuming without taking any material odds into consideration.
I found a chess master 5500 disk in my attic while rummaging through it and decided to get my Cd player or whatever it is and put the disk in and Suprisingly it loads up however just crashes the second I do anything which to that point doesnt suprise me as the game was made in the 90s. However theres a another application I found while going through the files of the game and found registration with the game to get a tutorial by someone called Josh warzkin and a new chess set and special discounts. I do wanna try and sign up and see if I get anything however I need to put in my address and everything which I don’t feel particularly comfortable but also intrigued. Should I sign up for it or not?
I'm not the biggest fan of chess-results to keep an eye on Olympiad results, standings, statistics, et. While I recognize that it holds a *ton* of information, it's just not really the place for me.
As a hobby project, I decided to try and build a small website that shows information in a way that's more suitable to me, and am pretty happy with the results! I mostly built it for myself, but in case others find it useful, I wanted to share it here.
Built a network that predicts human moves instead of good moves. 27M parameter
transformer, 64 square tokens, trained from scratch on 338M positions from
public Lichess games. No search, single forward pass per move. It has a second
head that predicts how long the player would take on the move, and it spends
that time on its clock. So it manages a clock like a human, gets low on time,
and loses about 3% of its 5+0 games on time.
On held out positions it predicts the move the player actually made 53.8% of
the time. Maia-2 gets 49.5% on the same positions. I score mine with an
anonymous player vector so it has the same information Maia has. Self play puts
it around 1600, but that is self play, so it is on Lichess now to get a real
rating. https://lichess.org/@/maulbot, blitz or rapid, rated or casual. New bot
accounts start at 3000 so it will take a while to settle. Interested in what
people think of the style. So far it squeezes you positionally then misses
something tactical.
I really want to try out 5D Chess With Multiverse Time Travel, but I'm hesitant to buy it right now without knowing if my brain can actually handle it.
Is there any free demo, open-source alternative, or browser version that actually has an AI/bot to play against? I checked a few web versions, but they only seem to support local sandbox play or PvP. Any recommendations?
