Create a vertical black gradient overlay on a background image
WHAT IT TESTS: CSS gradients, alpha channels, and layering. ANSWER: Use linear-gradient with rgba black stops, layer it over the image via stacked backgrounds or a pseudo-element. RED FLAG: Adding an extra div instead of native background stacking.
Which CSS background properties make a hero image cover its container?
Tests background-size keywords and aspect-ratio behavior. Lead with cover, note it fills the container by cropping while preserving ratio, unlike contain. Red flag: recommending 100% 100% or explicit lengths, which stretch and distort the image.
Explain em, rem, px and why rem is preferred for font sizing
This tests CSS unit semantics and accessibility. px is absolute; em compounds against its parent; rem is root-relative and predictable. rem respects user browser font settings without nesting issues.
How do you declare a custom font and apply it to headings?
This tests @font-face usage for custom web fonts. A good answer declares a font-family name and src URL inside @font-face, then applies that family to heading selectors.
Set paragraph text blue and background light grey, compare HEX, RGB, HSL
WHAT IT TESTS: CSS color syntax and tradeoffs between HEX, RGB, and HSL. ANSWER OUTLINE: Set color and background-color; HEX is compact, RGB is explicit, HSL is intuitive for lightness/hue. RED FLAG: Claiming HEX lacks transparency or equating RGB and HSL.
Explain :is() vs :where() specificity and when to pick :where()
Tests whether you treat specificity as architecture, not just syntax. :where() has zero specificity; :is() adopts the most specific argument's weight. Choose :where() for base resets or utility classes designed to be overridden. Red flag: calling them equal.
How is CSS specificity calculated for a complex selector?
This tests ID-CLASS-TYPE algorithm fluency. A strong answer gives the three-column tally, counts IDs, classes or attributes, and types in order, and notes combinators add zero. A red flag is counting combinators or mixing inline styles into selector scores.
What is margin collapsing? Give a sibling scenario and prevention.
This tests understanding of vertical margin combination in normal flow. A strong answer defines collapsing, gives a sibling paragraph example where the larger margin wins, and names a block formatting context or padding as prevention.
Describe the full CSS cascade precedence order
This tests deep cascade knowledge beyond specificity. A strong answer lists the six origins in order, notes !important reverses them, then layers, specificity, and source order.
How do class and ID selectors differ in specificity and use case?
WHAT IT TESTS: Your grasp of CSS specificity weights and selector architecture. ANSWER OUTLINE: IDs are 1-0-0 and meant for unique elements; classes are 0-1-0 and reusable. RED FLAG: Saying order alone decides specificity or using IDs for repeated components.
What color wins when an ID and class rule conflict?
WHAT IT TESTS: Your grasp of CSS specificity scoring beyond source order. ANSWER OUTLINE: Red wins; an ID scores 1-0-0 while a class scores 0-1-0, so the ID rule beats the class rule. RED FLAG: Saying the last declared rule wins or that order matters.
Explain the CSS box model: content-box vs border-box
Tests if you understand how width maps to rendered size. Good answers contrast content-box (350px + 10px border = 370px) with border-box (stays 350px) and note that four width:25% items break under content-box. Red flag: saying border-box includes margin.
CSS :has(): Query Parents and Previous Siblings
CSS :has() styles an element based on its children or later siblings, like highlighting a section with a featured card. Previously this required JavaScript. If unsupported, the whole selector block fails, so wrap it in :is() or use progressive enhancement.
Angular Universal: Hybrid Rendering for Faster Apps
Angular Universal enables hybrid rendering, letting you choose where each page is built: on the server (SSR), at build time (SSG), or in the browser (CSR). This improves load times and SEO. The footgun is misconfiguring routes, negating performance gains.
Nuxt Server Routes: Your Backend in a Folder
Nuxt Server Routes let you build a backend inside your frontend project. Create API endpoints by adding files to the `server/api` directory, which automatically get an `/api` prefix. The common footgun is forgetting this prefix difference with `server/routes`.
Svelte Transitions: Declarative UI Animation
Svelte transitions are declarative animations for elements entering or leaving the DOM. Use `transition:fade` on a modal or `crossfade` for items moving between lists. The footgun: they only run on mount/unmount, not on general state changes.
Angular Route Resolvers: Fetch Data Before Navigation
An Angular Route Resolver pre-fetches data, ensuring it's ready *before* your component renders. Use it to load critical data for a route, like a user profile, to avoid showing a loading spinner. The footgun: a slow resolver blocks navigation entirely.
Angular's `async` Pipe: Manage Observables in Templates
Angular's `async` pipe is a self-managing subscription for your templates. It unwraps values from Observables or Promises directly in your HTML, triggering updates on new emissions. It automatically unsubscribes, preventing the common footgun of memory leaks.
Angular's ng-template: Reusable UI Blueprints
ng-template defines a reusable UI blueprint that isn't rendered by default. Use it with ngTemplateOutlet to create configurable components, like passing a custom item layout to a generic list.
Angular Template Reference Variables: A #handle for Elements
A template reference variable is a handle to a DOM element or component within your template. Use the `#varName` syntax to grab an input's value or call a child component's method. Its scope is limited to the template where it's defined.