20 — Full-chain validation — recompute from genesis

The core rule is simple: do not trust the program state that existed while a block was being built. A validator should take chain data, start from genesis, and independently execute the same rules again.

NeedMoreCoin rechecks block height, previous-hash linkage, the recomputed block hash, proof-of-work target, transaction proof, positive amount, balance, fee, transaction nonce, minted reward, and final supply conservation.

The Korean advanced 사슬검증 function and English advanced validate_chain function make that replay explicit with data structures and functions. The pure Korean sentence version demonstrates the same principle with a separate set of verification-state variables.

nme run examples/needmorecoin-advanced.ko
nme run examples/needmorecoin-advanced.en

#Validation is not network consensus

This project implements a single-node chain-validation core. It does not claim to implement agreement among competing nodes. A real network still needs peer-to-peer propagation, fork choice and reorganization, persistent storage, difficulty adjustment or another consensus design, resource limits, testnets, and security review.

That distinction matters: “this chain is valid” and “many distributed nodes select the same chain” are separate problems.

Continue with the full NeedMoreCoin guide to compare all six syntax variants and extend the coin yourself.