Block Hash Chain: Tamper Cascade & Proof-of-Work

This simulation builds a real (if simplified) blockchain from scratch: five blocks, each holding transaction data, a nonce and a permanent reference to the previous block's hash, all mined so their combined hash starts with a target number of zeros. Edit any block's data and watch cryptographic hashing do its job — the block's own hash breaks instantly, and because every later block still points at its old hash, the tamper cascades forward turning the rest of the chain orange. Re-mining repairs the chain the only way a real blockchain can: re-linking and re-searching nonces block by block, exactly the proof-of-work cost that makes rewriting history expensive.