Programs that run themselves: how contracts execute, reading real Solidity, tokens as contracts, DeFi composability, famous hacks as lessons, oracles, and

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The W3D Team Author

Independent research on blockchain decentralization. Scores and methodology are maintained by the W3D Team.

1 · Core Lessons (CC-BY)

Programs That Run Themselves

A smart contract is a program stored on a blockchain that executes exactly as written — no operator, no pause button, no “we’ll look into it.” Deploy it, a

How a Contract Executes

Calling a contract means sending a transaction to its address with instructions (“swap X for Y,” “deposit Z”). Every node then re-runs your call to verify

Walkthrough: A Simple Storage Contract

No coding experience needed — read this like a recipe. This is the classic first contract (Solidity, Ethereum’s main language), storing one number anyone c

Tokens as Contracts: ERC-20 Anatomy

An ERC-20 token isn’t a coin object — it’s a contract holding a spreadsheet: addresses mapped to balances, plus rules for moving numbers between rows. “Sen

DeFi Building Blocks

Composability means contracts call each other: a vault deposits into a lending pool that prices via a DEX oracle. One user action can ripple through five p

When Contracts Fail: Hack Case Studies

Theory ends here. Each of these hacks taught the industry a rule — learn them cheaply, from history instead of your wallet.

Oracles and Off-Chain Data

Contracts can’t see the world — no prices, no weather, no scores. An oracle delivers outside facts on-chain as data contracts can use. Every DeFi protocol

Building Safely and What’s Next

Whether you’ll ever write Solidity or just want to judge protocols like a pro, this closing lesson is the safety doctrine plus the map onward.