// learn
What is Blockchain?
An interactive series. You learn each concept by doing it, right here in your browser. Nothing you type ever leaves the page.
Season 1 — What is blockchain?
Fingerprints, blocks, agreement, ownership. The mathematics, hands-on.
01 · hash.play
play nowWhat is a hash?
Type anything, watch its fingerprint change. Crack a PIN by brute force, watch a birthday-attack collision land, then mine your own block. Hashing is the atom of blockchain — start here.
02 · chain.link
play nowBlocks & chains
Build a block, break a blockchain, then repair it by re-mining. One edit invalidates all of history after it — see why, hands-on.
03 · consensus.pow
play nowConsensus & proof of work
Play the attacker: race the honest network to rewrite history, and inspect the assumptions behind confirmation risk.
04 · keys.sign
play nowWallets, keys & signatures
Generate a real key, sign a real message, verify it — then lose the key and feel exactly what 'not your keys' means.
Season 2 — Keeping the keys
Custody, from bedroom to boardroom.
05 · seed.words
play nowMnemonics & seed phrases
Real BIP39: turn coin flips into 24 words, sabotage the checksum, derive the seed — and learn where the words should live.
06 · wallet.temp
play nowHot & cold wallets
Slide across the storage spectrum, fall for a blind-signing trap, then simulate a cold-signing ceremony in one browser.
07 · vault.m-of-n
play nowMultisig — many keys, one vault
Explore a simulated 2-of-3 vault, collect signatures to a threshold, then lose keys on purpose. Bitcoin multisig vs Gnosis Safe, compared honestly.
08 · mpc.shares
play nowMPC — Signing Together
Split a secret with real Shamir sharing, see why splitting isn't signing, then inspect an illustrative threshold-signing flow.