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Concrete builds with clear ship criteria - not generic todos. Filter by track and difficulty, then open a project for architecture, requirements, and submission notes.
entries // 35 · beginner 10 · intermediate 13 · advanced 12
Category
Difficulty
35 projects in the library
Beginner5 daysbitcoin
BitcoinWallets
Address Format Lab
Generate and validate P2PKH, P2WPKH, P2SH-P2WPKH, and P2TR addresses from the same key material. Explain each encoding.
Skills
Bech32Base58CheckKey derivation basics
Prerequisites
Keys & Addresses · SegWit & Bech32
Beginner3 daysbitcoin
BitcoinWallets
BIP-21 Payment URI Tool
Build and parse bitcoin: URIs with amount, label, and message. Generate QR codes merchants can scan.
Skills
BIP-21QR encodingURL query parsing
Prerequisites
Keys & Addresses
Beginner1 weekbitcoin
Bitcoin
Bitcoin Script Puzzle Kit
Solve and author locking scripts with OP_IF, hash locks, and timelocks. Verify spends on regtest.
Skills
Bitcoin ScriptOpcodesRegtest
Prerequisites
Bitcoin Script · Transactions
Beginner5 daysbitcoin
Bitcoin
Block Header Inspector
Decode block headers, verify proof-of-work targets, and walk merkle proofs for a chosen transaction.
Skills
HeadersMerkle treesDifficulty bits
Prerequisites
Blocks & Chain
Beginner4 dayslightning
Lightning
BOLT11 Invoice Decoder
Decode Lightning invoices into amount, payment hash, expiry, route hints, and feature bits. Round-trip encode a test invoice.
Skills
BOLT11Bech32TLV tags
Prerequisites
Invoices · Lightning Overview
Beginner1 weekbitcoin
BitcoinWallets
Coin Selection Playground
Implement largest-first and branch-and-bound style selection. Visualize waste, change, and fee tradeoffs on a fixed UTXO set.
Skills
UTXOsAlgorithmsFee math
Prerequisites
UTXO Model · Mempool & Fees
Beginner2 daysbitcoin
BitcoinInfrastructure
Hello Regtest
Spin up bitcoind in regtest, mine your first blocks, fund a wallet, and print a confirmed balance with Core RPC.
Skills
Bitcoin CoreRPCDocker or local install
Prerequisites
Developer Environment
Beginner1 weeklightning
LightningWallets
LNURL-Withdraw Kiosk
Implement a tiny LNURL-withdraw endpoint that hands out small testnet payments from a pre-funded node.
Skills
LNURLHTTP callbacksInvoice creation
Prerequisites
LNURL · Invoices
Beginner5 daysbitcoin
BitcoinInfrastructure
Mempool Fee Thermometer
Poll fee estimates and mempool size, then chart next-block vs economy rates so users pick a sensible feerate.
Skills
REST or RPCSimple chartsFee units (sat/vB)
Prerequisites
Mempool & Fees