Box model, cascade, units, and layout primitives you will actually use in interviews and production.

One-dimensional layout: alignment, distribution, wrapping, and the gotchas interviewers love.

Two-dimensional layout: tracks, areas, fr units, and auto-fit patterns.

Daily commands, branching, undo patterns, and interview-safe explanations.

Types you need in interviews: unions, narrowing, generics, and utility types.

useState, useEffect, useMemo, useCallback, useRef — mental models and footguns.

Patterns, groups, flags, and practical examples for validation and parsing.