Is Chaindoku free?+
Yes, entirely. Every case, the glossary and the hints are free, with no ads and no hidden fees.
Do I need to know crypto?+
No. On-chain terms dress up the investigation, but everything is solved with the logic of the grid. The glossary explains each word (block, hop, cluster, multisig…) in one sentence.
Is Chaindoku like sudoku?+
It shares its DNA: a grid where every row and every column holds exactly one address. The difference is the story. Instead of numbers, you deduce where the suspects stand and which one shares the victim's cluster: it feels like cracking a case, not filling in a table.
Do I ever have to guess?+
Never blindly. Every case is checked by a solver: one solution, every clue necessary. In Easy and Medium, everything follows by deduction, with no hypothesis. In Hard, you sometimes have to try a cell and see that it leads to a contradiction: their number is shown on the case. If you're stuck, the Hint button shows you the next deduction.
What do you learn by playing?+
Blockchain basics (blocks, wallets, fees, smart contracts…), how to recognize the most common scams, whose tricks each case reuses, and how to reason by deduction. The tutorial, the initiation and the blockchain discovery lay the groundwork; the glossary explains every term in plain words.
Do I need an account?+
No. An anonymous guest account is created automatically on your first case, with no email and no password. To find your progress on another device, link an email to it from the Sign in button.
Is this investment advice?+
No. The cases are fiction: characters, addresses and projects are made up, and nothing in the game is financial information or advice.
A sudoku that runs the investigation
Chaindoku is a deduction puzzle where every case is a miniature heist on the blockchain. A treasury has been drained, an address has vanished, and a handful of suspect addresses circle around. Instead of filling a grid with numbers, you place every suspect back on the ledger, armed only with logic and a stack of on-chain evidence.
The grid reads like a trace: columns are blocks, in the chronological order of signatures, and rows are hops, the depth of the fund flow. As in sudoku, each address holds its own row and its own column. The colored zones are clusters (Vault, CEX, DEX…) and, once the grid is complete, only one address shares the victim's cluster: that is the one that drained the treasury.
Chaindoku also has an educational aim: case after case, you pick up real on-chain concepts (blocks, clusters, multisig addresses, oracles, bridges…), explained in the glossary.
Learning by playing
Chaindoku starts from a belief: you understand the blockchain better by running an investigation than by taking a course. The path is gradual: a two-minute tutorial, the Initiation (five short lessons, one rule at a time), then the blockchain discovery, five small cases that each introduce a crypto notion (wallet and seed phrase, fees, confirmations, smart contract, stablecoin) in a short box.
The cases are inspired by real scams: fake support, fake recruiter, SIM swap, fake giveaway, booby-trapped browser extension, rug pull, Ponzi scheme… Solving them teaches you to spot their tricks, and to be wary of them. Every technical word underlined with dots explains itself with a tap, and the glossary gives a plain definition, free of jargon.
You also learn to reason. In Easy and Medium, everything follows step by step, with no hypothesis. In Hard, you sometimes have to try a cell and see that it leads to a contradiction, and the number of these hypotheses is shown on the case. The Hint button doesn't hand over the answer: it shows where to look, then why, like a teacher who guides rather than corrects.
How to play online
Each case hands you a briefing, a grid, suspects and a column of plain-language clues. One signed in block 2, another sits on an RPC node, a third is one hop deeper than the Quiet Whale. Select a suspect card, tap a cell to note a hypothesis, hold to confirm. Cards turn green when their clue holds and red as soon as it breaks.
Tools help you along: block an impossible cell, undo the last move, erase, and a Hint button that starts from your grid: it shows you where to look, then why, then the cell if you ask (a hint reserve that refills as you play, one to three cells per case depending on difficulty, and a game with a revealed cell doesn't count for your record). The built-in glossary explains every term of the grid and the legend, so you can follow the trail without opaque jargon.
Fair cases, checked by the machine
Beneath the on-chain noir mood runs a real logic engine. Every case goes through a solver that guarantees one solution and only one, and checks that every clue matters: none is decorative. You never need to guess blindly: patient reasoning always leads to a single, provable answer.
The stories are handwritten fiction: a midnight rug pull, a rigged DAO vote, a fatal flash loan, a corrupted oracle, a bridge between two chains, a bot sandwich… Each file has its own setting, roles and markers.
From easy to downright devious
The ledger currently holds 69 cases: 35 easy, 21 medium and 13 hard, on grids from 4×4 to 12×12. Easy cases wrap up in a few minutes and make a perfect way in.
Hard cases earn their name. They don't rely on exotic clues but on long chains of deductions, a few hypotheses to check (their number is shown), suspects that only settle at the very end and openings that refuse to give you an easy first move. Every solved case keeps your best time, ready to beat on a replay.
Free, no ads, no forms
Chaindoku is free to play in the browser, on phone, tablet or computer. Nothing to install, no ads, no paywall, no email or password to hand over.
From your first case, an anonymous guest account records your games and shows you in the leaderboard, as an anonymous investigator or under the nickname of your choice. Link an email to find your progress on all your devices. The game is available in French and English.