One site, two boards. They share the same bots, and you can switch between them at any time.
♟ Blundermind
Visualization training
A board that draws what a stronger player sees. Thirteen overlays, among
them threats, pins, forks, unprotected pieces and weak squares, light up
while you explore a move, so you can check what you pictured against
what is really on the board.
Ghost moves can show the likeliest replies before you commit, and Maia
move odds show afterwards how human players weighed the move just played.
Play a bot, play a friend online, or just explore.
♞ Build-A-Bot Chess
Customized bots
Build an opponent instead of picking one. Start with the engine:
Maia 3, a neural net trained on human games that goes wrong
the way people do; Flounder, built on Stockfish and set with a
rating dial; or a Hybrid that mixes engines and ratings move by move.
Then shape it: a personality that pulls toward the moves it likes within
a centipawn budget, an opening repertoire, how long it thinks, and how it
cracks under time pressure. Name it, save it, share it, and play it on
the pro board, a clean tournament view with no visualization aids.
+ off · green ✓ while exploring · dark ✓ always on
OffWhile exploringAlways on
Hold the dashed buttons — they spring back on release.
One move deeper
The bot’s likeliest replies, drawn faintly while you explore a move.
⚔ Inactive & unavailable during 2-player games — engine hints would undercut human-vs-human play.
⚠ Maia3 model not downloaded
Maia is what makes ghosts and the Maia bots feel human. Until it
is downloaded, every one of them quietly falls back to Flounder — which is
rated, so the opponent stays roughly the strength you asked for.
♚
Black
—
Notation▾
No moves yet
♔
White
—
🤖 Play / Build Bot
⚔ 2-Player
💾 Save game
▶ Load game
💾 Save bot
⚑ Resign
½ Draw
⇅
🎨
⚙
Promote pawn to:
Board vision
Tap to cycle · swipe right to close
About & Feedback
Also on the web
This app is an adaptation of the browser-based version.
Some of the board visualizations have more room to breathe on a larger screen.
Feedback and suggestions have been extremely helpful. Thanks to everyone for your time and insights.
Thank you — feedback received! ⚟
Or email blundermindchess@gmail.com — better if you want to attach a screenshot or a PGN, or if you’d like a reply.
About
Most chess games I play are decided on blundered pieces. I created this site in the hopes that I could see what it was like to play a game that was decided by strategy instead of blunders. I still blunder, but at least the number of blunders is reduced a bit when there is a big red circle around the queen when I hover it over my intended square.
Build-A-Bot / Bot Builder
While I most enjoy playing people in person, I find playing strangers online oddly stressful, so I added in the feature to play against bots. The problem with the bots I’ve found is that they don’t feel time pressure, and their behavior is often sporadic in an unsatisfying way. I’ve tried to make the bots customizable in a way so that I have more control over how the bot will play. This became a deeper and more interesting rabbit hole than the initial visualization design.
Blundermind / Visualization Board
I struggle with “getting a grip on the board” (to steal a useful phrase from the Chess Dojo), so while my intent was to blundercheck moves so that I would see if I were hanging my queen, I’m finding that it is showing discovered attacks and potential forks that I didn’t see at all (you can probably infer my rating at this point). I think this site could be a useful learning tool if the visualization aids are set to provide immediate feedback after careful assessment and calculation, not as a blunder avoider that just circles some hanging pieces while potential moves are explored by dragging the pieces around. Admittedly, I have found the latter to be interesting as well.
Also included in my numerous struggles is the ability to predict my opponent’s response, so I added a feature to show two potential responses by making two engine calls. I would caution that this feature should only be turned on if you have already actively calculated your opponent’s likely next move.
The site does not include any engine analysis or indicators to show if a move is “good or bad” during game play or exploration. Each game can be downloaded and analyzed in Lichess or a website of your choice. Similarly, the PGN of any game can be uploaded and explored or played out here.
Privacy
Blundermind / Build-A-Bot uses no cookies or tracking, and there are no accounts. Games in progress and settings are saved on your own device so you can close the tab and pick the game back up — that stays on your device, is never sent anywhere, and clearing your browser data removes it. The board set up/configuration and customized bots can be downloaded and stored, then uploaded for future use. The one thing that does leave your device is a feedback message, if you choose to write one above. This site is open source, available on GitHub. Full details in the privacy policy.
Every rating on this dial was measured by playing it against Maia at the same rating — 796 games in all.
🎣 Flounder is built on Stockfish (GPL-3.0). It scores every legal
move with Stockfish, then samples how much the turn should cost from the error
curve in Regan & Haworth, Intrinsic Chess Ratings — so it makes
human-shaped mistakes instead of playing a weakened search.
4
Engine degrades from starting level → this level when clock is low
NoneHigh
Always plays at selected level
1.0
🧠 Real Maia3 — human-like neural network (600–2600 Elo).
Download once (~44MB), runs in your browser. Uses ~150–200MB RAM while active. Falls back to Flounder at the same rating if not downloaded.
