Twelve explained decisions about CSS constraints, font and motion fallbacks, event ordering, workers, and cleanup. Choose one response, inspect its explanation, and revisit the lesson for a missed boundary.
Related lessons
Grid, Flex, and Intrinsic Size Contracts; Container Queries for Reusable Panels; Cascade Layers and Design Token Ownership; Font Loading and Motion Fallbacks; Event Loop Tasks, Microtasks, and Paint; Workers, Messages, Transfer, and Cancellation; Cooperative Main-Thread Scheduling; Browser Memory and Resource Lifecycles.