Blockchain Foundations
Blockchain Foundations — Start with the physical reality of nodes, RPCs, and gas.
Figure out where data lives, how RPCs connect your app, and why gas isn't arbitrary—before writing a single line of Solidity.
Why Blockchain Exists
Start with the problem, not the technology. Centralized trust failure, the double-spend problem, and when NOT to use blockchain.
The trust problem — why do we need banks?
Double-spend problem. Why digital money failed before Bitcoin. The human cost of centralized trust.
Centralized vs decentralized systems
Single point of failure. Censorship. Downtime. Why decentralization solves specific problems.
What blockchain actually invented
Not just a database. A consensus mechanism for untrusted parties. The Nakamoto breakthrough.
Where blockchain SHOULD NOT be used
The most important lesson in T0. If a database works, use a database. Blockchain is a trust primitive.
How Blockchain Actually Works
What is a block. What is a chain. How consensus works. What actually happens during a transaction — visually.
What is a block — data structure deep dive
Previous hash, merkle root, timestamp, nonce, transactions. Why the previous hash chains blocks together.
Transactions explained visually
From, to, value, data, signature. What happens when you press send. The mempool.
Consensus — how strangers agree
Byzantine fault tolerance for humans. Why miners/validators exist. The economic incentive design.
PoW vs PoS — why Ethereum switched
Energy cost of mining. Proof of Stake economics. Validators, slashing, finality.
Networks & Storage
Mainnet vs testnet. Ethereum vs Polygon vs L2s. RPC explained. Where blockchain data actually lives.
Mainnet vs testnet — NOT the same thing
Why ETH costs $3,000 but Sepolia ETH is free. Chain IDs, faucets, token economics, and why Polygon is cheap. The value mental model every beginner needs.
RPC explained — your app's phone line to the blockchain
ABI as translator, RPC as phone line, EVM as execution environment. The three invisible layers between your code and the blockchain.
Ethereum vs Polygon vs Base — when to deploy where
Gas costs, finality, ecosystem, liquidity. How L2s work conceptually.
Wallets & Identity
Private keys, public keys, seed phrases, signing — the cryptographic identity system.
Why Web3 needs wallets — identity without a server
Why a faucet asks for an address, why an address requires a wallet, and why a wallet is not a bank account. The rubber stamp vs library card mental model.
Private keys, public keys, addresses
Asymmetric cryptography for humans. Your private key IS your identity.
Wallets don't store coins — the biggest mental hurdle
Coins live on the global ledger. Your wallet is just a bundle of signing credentials.
What MetaMask actually does — and doesn't do
It's a key manager, not a vault. Coins live on-chain, not in MetaMask. UX challenges.
Seed phrases — brilliant security, terrible UX
BIP-39 mnemonic. HD wallet derivation paths. Why 12 words = full account control.
How signing actually works — cryptographic verification
ECDSA signatures. Private keys sign, public keys verify. Why signing does not move gas.
Anatomy of a transaction [Optional Deep Dive]
EVM transaction payload, fields, signatures, gas fees, and network propagation.
Gas & Transactions
What gas actually is, EVM opcode pricing, base fees, priority fees, and transaction failure modes.
Why gas exists and how it's calculated
EVM opcodes cost computation. Base fee + priority fee. EIP-1559 explained.
Base fee + priority fee — EIP-1559 explained
How gas pricing actually works post-London upgrade. Why base fee burns. Why priority fee goes to validators.
Why you pay gas even when the transaction fails
EVM still executed. The gas meter ran. Analogous to a taxi meter running.
Why Polygon is cheaper than Ethereum
Block space supply and demand. L1 vs L2 economics. Why gas price is not fixed.