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Start here for low-level design
Entities, state machines, replaceable policies and contracts you can test. The classic machine-coding round problems.
Model spots, tickets, and pricing with clear responsibilities and safe allocation.
Model selection, payment, dispensing and refunds with guarded state transitions.
Separate board rules, turn handling and game state for a testable game engine.
Model card identity, fair shuffling and atomic dealing with injectable randomness.
Model simultaneous movement, food growth and body collisions with clear invariants.
Model titles, physical copies, loans and reservations without double lending.
Compose structured logging, redaction and bounded asynchronous output.
Model cart mutations, version checks and reproducible price quotes.
Evaluate composable discount rules with exact arithmetic and atomic redemption limits.
Split expenses fairly with exact money arithmetic and an auditable ledger.
Execute versioned transition tables with pure guards and atomic effect intent.
Define subscription, dispatch and error semantics for a reusable event dispatcher.
Model reversible commands, history branches and atomic grouped edits.