Questions
What is this?
Enter any chess.com or Lichess username and you get to play a bot modelled
on that player. It learns their real opening choices from their actual games,
and makes mistakes sized to their level rather than generic engine mistakes.
How does it work?
Their recent blitz games are pulled from the platform's public API and
analysed in your browser. The openings are genuinely theirs — the shadow plays
the moves that player actually chose, weighted by how often they chose them.
Once play leaves their known repertoire, Stockfish takes over. How often the
shadow errs, and how badly, is calibrated to their rating and adjusted for the
time control you pick, so a strong player's shadow makes strong-player mistakes
rather than beginner ones.
Is any of this stored? Is it private?
Nothing is stored and nothing is sent to us. The games are
fetched straight from chess.com or Lichess to your browser, analysed there, and
discarded when you close the tab. No account, no login, no tracking of who you
look up.
Only data those platforms already publish is used — the same information
anyone can see on a public profile. If a player's games are public, their shadow
can be built; nothing hidden is accessed.
How accurate is it, really?
It's a statistical approximation, not a trained model of a person. The
openings are real data. The mistakes are calibrated to be plausible for someone
at that rating — they are not that player's specific mistakes, and the rating
bands behind the calibration are reasoned estimates rather than measured data.
The opening book also runs out once you play something that player hasn't
faced. From there you're facing a well-calibrated engine, not a replica.
What else can I do here?
Pick a time control (1+0 through 10+0, or no limit) before starting. During or
after a game you can Save PGN, or send the game straight to
chess.com or Lichess to analyse it. The engine strength slider adjusts how
strongly the shadow plays between book moves.
Share links carry the player you looked up, so sending someone a link opens
that same shadow for them.
Something isn't working
"No blitz games found" — that account has no recent blitz
games in the window selected. Try a longer range, or the other platform.
A warning about a small sample — there were too few games
to build a representative picture. The shadow still works, just less faithfully.
A red notice about the chess engine — Stockfish didn't load
in your browser. The game still works but plays noticeably weaker; a refresh
usually fixes it.
Anything else, please use Send feedback below — it goes straight to me.