Interactive tech lessons
中文Every lesson has Beginner and Advanced explanations, animations you can control, and a quiz at the end.
HTTP, step by step
Follow a request from DNS to the rendered page, try every HTTP method against a mock API, and test yourself.
Designing good APIs
Fix badly named endpoints, choose the right status codes, see why cursor pagination wins, and learn which changes break clients.
SQL, hands on
Build queries by clicking, watch JOINs match rows and GROUP BY fill buckets, and learn the order a query really runs in.
Designing a database
Break a spreadsheet-style table and normalise it, model relationships, race a full scan against an index, and crash a bank transfer with and without a transaction.
Formal verification
See why tests miss rare bugs, write specifications, model-check a locking protocol state by state, and prove a loop correct with an invariant.