Solidity Fundamentals
BeginnerMaster the basics through 7 progressive courses: variables, functions, data structures, inheritance and design patterns.
Variables & TypesFunctionsMappingsStructsEventsModifiersInheritance
~200 exercises
1000+ Solidity Exercises
Learn by practicing with interactive exercises, security challenges, guided projects and a built-in IDE. From complete beginner to audit expert.
Explore our exercise categories
Security & Smart Contract Audit
Intermediate60 security challenges to identify and fix vulnerabilities: reentrancy, overflow, access control, front-running, and more.
ReentrancyInteger OverflowAccess ControlFront-RunningDelegatecallDoS
60 challenges
Gas Optimization
ExpertAdvanced gas optimization techniques: storage packing, short-circuiting, unchecked math, assembly, and more.
Storage PackingUnchecked MathAssemblyMemory vs StorageCalldataCustom Errors
~80 exercises (3 levels)
Reverse Engineering
ExpertDecode EVM bytecode, analyze unverified contracts, understand ABI encoding and master static analysis.
Bytecode AnalysisABI EncodingEVM OpcodesDecompilationStorage Layout
~60 exercises (3 levels)
Unit Testing & Fuzzing
IntermediateLearn to test smart contracts with Foundry and Hardhat. Coverage, fuzzing, integration tests, and mocking.
Foundry TestsFuzzingInvariant TestingMockingCoverageHardhat
~70 exercises (3 levels)
Guided Projects
All levelsBuild real projects from scratch: ERC-20, NFT Collection, DEX, DAO, DeFi Vault, Multisig Wallet.
ERC-20 TokenNFT CollectionSimple DEXGovernance DAODeFi VaultMultisig
14 projects (9 standard + 5 Pro)
Timed Challenges
All levelsTest your speed and accuracy with timed challenges. 3 levels: Beginner (30min), Intermediate (20min), Expert (15min).
Speed CodingQuick DebuggingGas OptimizationLeaderboard
~50 challenges (3 levels)