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Chess game review

Know why you lost.

Chess engine analysis shows you the move you missed. Cortex explains why you missed it, what the better move actually does, and how to think differently next time.

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Teaching Moment
25. … Rxd3

−1.7 → +0.0·You were ahead, and you let it slip.

A pawn recapture can do more than a rook recapture.

1

What happened

You captured the bishop with your rook, which does win the piece and levels the material. The rook lands on d3 with some activity — it attacks c3, which is defended by only one piece against your two attackers, and it controls the d-file down to d1. But White's best reply is Qb3, which immediately stabilizes the position and takes the pressure off. The eval impact is clear: an advantage you had built up simply faded away.

2

The concept

The key concept here is that how you recapture matters enormously. You had two ways to take on d3, and they lead to very different positions. The rook recapture gives you a piece of wood and a rook on an open file. The pawn recapture does something more: it puts a pawn on d3 that jabs at both c2 and e2 simultaneously, keeping White's queen and rook tied down and maintaining the pressure you had already earned. That kind of persistent, nagging threat is hard to deal with — it forces your opponent to react rather than consolidate.

3

The better move

With exd3, the best-play line continues with White retreating the rook to a1, then your queen swinging to e4, White's queen going to a2, and your king stepping to g7 — a sequence where Black keeps the initiative and improves piece by piece. The pawn on d3 acts as a wedge that keeps White's pieces awkward, whereas after Rxd3 White gets to reorganize freely. When you have a choice between recaptures, ask which one keeps your opponent on the back foot.

The problem

You're not a beginner. You're stuck.

You know what a pin is. You understand king safety. You've watched the videos and done the puzzles. And your rating has sat in the same 100-point band for six months — you genuinely can't figure out why.

After every loss you do the right thing. You open the analysis. You see the arrow. You see the eval swing. You nod. You close the tab. Two weeks later, a different opening, a different opponent — and something familiar happens. The position collapses. You open the analysis again.

This isn't a discipline problem. Engine analysis was never designed to teach you. It was built to show you what Stockfish would have played. Those are not the same thing.

The engine

“Inaccuracy. −1.7. Best move was exd3.”

An arrow points at the answer. It marks the door you should have walked through — and says nothing about why you missed it.

Cortex

“You grabbed the bishop with your rook. Recapture with the pawn instead — exd3 makes a passed pawn that does the attacking for you.”

A reason you can carry into the next game. The same idea, explained — so the door isn't a surprise next time.

You've probably tried everything

They told you that you blundered.

Accuracy scores. Puzzle Rush. Brilliant YouTube channels about positions you'll never reach. Maybe a few months of a chess-improvement app. They'll tell you your accuracy was 74% and that you should work on knight forks.

What they won't tell you: why your king move on move 45 was wrong — not the check itself, but that you moved your only defender away from a pawn that was already hanging. That's not a stat. That's understanding.

Cortex doesn't claim to be revolutionary. It does one specific thing well: it explains your games to you in plain English, the way a good coach would.

Accuracy: 74%Puzzle Rush“You blundered”Eval bar: −1.8Work on knight forks12,000 puzzles solvedOpening trainer

Your blind spots

Every player has patterns they can't see.

For every moment where the position actually shifted, Cortex gives you three things — the same three a coach would walk you through at the board.

01

What happened

Not just “this was a blunder.” A plain-English account of the position — which pieces were active, what the real threat was, why your move looked reasonable and why it wasn't.

02

The concept

Every mistake has an idea behind it. King safety in sharp endgames. Checks that waste tempo. Cortex names the concept — so you recognize it in any game, not just this one.

03

The better move

Not just the move — the plan behind it. What exd3 creates, what it threatens, what it keeps alive. The reasoning, not the arrow.

That's what Cortex can see in the position. What it can't see is what was going through your head when you played — and that half is just as much a part of getting better.

Reflection

What were you actually thinking?

The honest answer is more valuable than the right one.

None of them ask what was in your head when you played the move — what you were worried about, whether you felt in control or were just reacting. Cortex asks, right there at the move. Write down what you remember thinking. Then read it next to what the position actually demanded. The gap between the two is the thing you came to learn.

Your reflections are private by default — yours alone. Share a note when you want to: with a coach, a training partner, a friend who'll tell you the truth. Optional, always: the review works whether or not you write a word.

  1. 23.Bxe5Qxe5
  2. 24.Ra7Nd3
  3. 25.Bxd3Rxd3
  4. Your Note for Rxd3edit

    i knew this was a big moment and i figured since i already doubled their kingside pawns, i would go after the c3 doubled pawn weakness. ugh turns out this wasn't the right move

  5. 26.Ra1Qxc3
  6. 27.Qxc3Rxc3

Right there, at the move.

On your time
Pull up the game you just lost
Read the review when you have time
The understanding compounds

Built for real life

For players who fit chess around a full life.

You don't have three hours a night to study chess. You have the small windows — before bed, a lunch break, the train home, between rounds — and a review only takes a minute of one.

Playing is how you improve — but only if the games don't go to waste. The point isn't more games. It's actually learning from the ones you play. Cortex works on your schedule — the understanding compounds, even when your study time doesn't.

One place for all your chess

Every game you play, in one library.

Chess.comLichesspull automatically+the tournament games you add

Wherever you play — Chess.com, Lichess — your games pull in on their own. Tournament games you add yourself. No exporting, no hunting through tabs. It all just lives in one place, ready when you are.

Free, always

Explanation shouldn't be paywalled.

Three game reviews a day, free — not for 14 days, not for your first three games and then a paywall. Three more tomorrow, for as long as you play chess. Engine analysis has always been free. If Cortex can't earn your trust on a free review, it doesn't deserve your subscription.

$0Per review
3Reviews a day
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Three games a day, explained so they actually click — that part's free, always. Getting better is what comes next: replay the moments that cost you so you stop repeating them, and step back across all your games to see the player you really are — then turn those weak spots into strengths.

Replay

Reading about a mistake isn't the same as fixing it.

So Cortex makes you play it again.

Understanding a mistake while you read the review is recognition — and recognition fades. The fix only sticks when you have to produce the move yourself: cold, on the board, with nothing pointing at the answer. So before you sit down to play again, Cortex hands you back your own worst moment and asks the only question that makes it stick — your move?

01

You play the move, you don't read it.

No arrow, no multiple choice. Producing it from memory is what burns it in.

02

It's your moment, not a puzzle.

The exact position you lost, pulled from your own game — not a tactic from a position you'll never reach.

03

Right before you play again.

Not buried in a history tab. You walk into the next game having just re-felt the thing that cost you last time.

Replay · before you play again

You let the advantage slip here. Play the move that keeps the pressure.

The move that cost you becomes the one you've already practiced.

Beyond one game

The mistake you don't even know you're making.

A pattern only shows up when your games sit together — one slip looks like bad luck until you see it happen across game after game. One review shows you a slip. But the thing actually holding your rating down is the slip you keep making — the same idea costing you game after game, invisible because you only ever see it one game at a time. Play a few in a sitting and Cortex reads them together, names the pattern, and shows you what to work on next. That's how a weak spot becomes a strength — you finally know which one to fix.

“Across today's 6 games, the same idea cost you three times: you traded off your good bishop to win a pawn, then had nothing to attack with. One thread, one fix.”Day recap · Plus

Pricing

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Three games a day, reviewed and explained.

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  • Every game in one place — Chess.com, Lichess, and the ones you played over the board
  • Teaching Moments, not engine output — your turning points explained in plain language, with the better move on the board next to yours
  • Know where your time goes — opening, middlegame, endgame, and what to change so you're not deciding the game with none of it left
  • Keep notes on your own moves — private by default, or shared when you want a second opinion
  • Send a game to a coach or a friend — one link, no account needed, both sides' moments included
PLUS
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Pay once, keep Plus forever — founding price for early members.

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  • Everything in Free
  • Review as many games as you want — no three-a-day cap, so a whole tournament can go through in one sitting
  • Twice the Teaching Moments — six turning points per side instead of three, catching the quiet mistakes that lose the game slowly. Your old reviews deepen too.
  • Recall drills — replay your own critical moments before you sit down again, so the fix is in your hands, not just in your notes
  • Recaps — a day, a week, or a whole tournament read as one story instead of separate games, ending in the one thing to work on next

Questions

Straight answers.

What does Cortex Chess do?

Cortex Chess reviews the games you already play — on Chess.com, on Lichess, or over the board — and explains why you lost, in plain English.

After you lose, you usually think you know what went wrong. Sometimes you're right. But often the move you feel bad about isn't the move that lost the game, and the one that did happened ten moves earlier, back when the position still looked fine. That's the hard part to see on your own, and it's the part you keep repeating.

Cortex finds the moves where the game really changed. It puts the better move on the board next to the one you played, explains what that better move does, and explains what you'd need to look for to find it yourself next time. Knowing you made a mistake doesn't help much. Knowing why you made it is the part you can use in your next game.

That's the reason to start using Cortex. Here's what makes players stay: you can write a note on any move while the game is fresh, you can talk it through with a friend or a coach on that exact move, and every week your Weekly Recap pulls the week together — what kept going right, what kept going wrong, how you handled your clock, and the one thing to watch for in your next game.

What is the difference between game analysis and engine analysis?

Engine analysis is what a chess engine gives you: for any position, the strongest move and a number saying who's better and by how much. It's fast, it's correct, and it has no idea what you were thinking.

A game review starts from that and asks the questions a person would ask instead. Which of these mistakes actually lost the game? Why did the move look good to you at the time? What would you have needed to see?

An engine says move 24 cost you two pawns. A game review explains that you traded off your only good piece because you were scared of an attack that was never coming. Only one of those helps you play better next time.

How is this different from the free analysis on Chess.com or Lichess?

Those give you engine analysis, and they give it away, which is really useful — Cortex uses an engine too. The difference is what happens next.

They mark every weak move in a 40-move game and leave you to figure out which ones actually cost you. Cortex picks the moves that decided the game and explains each one in plain sentences: what you played, what was better, and what you'd have had to see.

And we don't put that behind a paywall. You get three game reviews a day, free, forever.

Do you have opening courses or spaced-repetition training?

Not yet. Right now there are no opening courses, no puzzle rush, and no spaced-repetition trainer in Cortex. We want to add training like this and we're taking our time working out the best way to do it, because a drill that doesn't come from your own games is just more homework.

Today Cortex works on the games you've already played. If you want to drill openings or practice puzzles in the meantime, Chessable, Chess.com and Lichess all do that well. Cortex Plus does include recall drills, and those put you back in your own positions from your own games.

Does it work with Chess.com and Lichess? What about games I played over the board?

All three. Enter your Chess.com or Lichess username and your games pull in on their own, including new ones as you keep playing.

For a game you played over the board, either play the moves onto a board in the app or paste the PGN. Your tournament games get reviewed exactly the same way your online ones do. Most tools can't do that at all, and those are usually your longest and most serious games.

Do I need an account to try it?

Yep, you do — and it's completely free. You'll start by entering your Chess.com or Lichess username. Cortex goes and finds your games, and puts your most recent loss on the board right in front of you. While that's happening you add an email and a password. No credit card.

Finish that and you land straight in the review of that game, already running.

What does Cortex Chess cost?

Cortex is free, and game review stays free. Three game reviews a day, every day, for as long as you play.

Cortex Plus is a single twenty dollar payment — not a subscription, nothing to renew — and that's a founding price for early members. With Plus you can review as many games a day as you want, and every review finds six key moves per side instead of three. You also get drills that put you back in your own positions, and recaps that read a day, a week or a whole tournament as one story instead of separate games.

Is free forever actually free forever?

Yes. Not fourteen days, and not a trial that stops right when it gets useful. Three game reviews a day are part of the free plan and they stay there. Use all three and you get three more the next day.

Plus adds more on top of the free plan — as many reviews a day as you want, plus drills and recaps. It doesn't take anything away from it.

What rating is Cortex Chess for?

Cortex is for players chasing their next rating milestone on the way to 2000. Whether that's breaking 1000, getting past 1400, or finally holding 1800, the thing in your way is usually a mistake you keep making and can't see on your own. That's what Cortex finds.

If you're brand new to chess, play a few hundred games first. There aren't patterns to find yet. There will be.

Do I need to understand engine evaluations to use it?

No, and that's most of the point. Cortex explains your game in sentences instead of numbers like −1.7, and puts the better move on the board beside the one you played, so you can see the difference rather than read a score.

The engine's number is still there if you want it, and you can hide it if you'd rather read your game without it.

Can I take notes on my own games?

Yes, and it's a big part of what makes a review worth reading again later. Open any move and write down what you were actually thinking — your plan, the attack you were worried about, the move you almost played instead. It takes a couple of taps, right on the move, so there's no separate document to keep updated.

Your notes are private to you unless you decide otherwise. When you want a second opinion, you can pull a friend or a coach into a discussion on that one position, so you're both talking about the same move instead of sending someone a whole game and hoping they find it.

Can my coach use this?

Yes, and it's one of the best ways to use Cortex. Connect with your coach and they can see all of your games, not one at a time, and work through them with you. They land on a page built for a coach rather than a copy of yours.

They can comment on any move, and those exchanges stay between the two of you. A coach sees your notes, because showing a coach your thinking is the whole point.

If you only want to share one game, send it as a link instead. You can take any link back and it stops working right away.

Can I play chess on Cortex?

Not yet, and it's the thing we're most excited about. Today Cortex reviews games you play somewhere else — Chess.com, Lichess, or over the board.

Playing on Cortex is coming. It's a different kind of practice when the app that found your mistake can put you back in that exact position and let you play it out properly. Make an account and we'll tell you the moment it's ready.

What happens to my games and my data?

Your games stay in Cortex. We don't sell your data and we don't hand it to anyone else.

Every game you review is yours alone until you decide otherwise. When you share one, you're sharing that single game through a link you can revoke — never your account — and your private notes stay out of a link to a friend unless you choose to include them.

Cortex is in early access

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