FrontendHaltCSS·Advanced·Conceptual·1 min read
How does box-sizing interact with a percentage width?
Short interview answer
A percentage width is still resolved against the containing block first under either model; box-sizing then determines whether that resolved pixel value represents the content area alone or the content-plus-padding-plus-border total.
Key takeaway
Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.