▸case-01 Our web dashboard canvas chart animation drops frames on standard 60 Hz desktop displays. A developer suggests setting a frame execution budget of 50ms per frame so the CPU has enough time to calculate heavy data points. What frame execution budget limit should the team enforce to ensure smooth 60fps rendering? | pass→fail | 8,590 | 10,156 | +18% | 1 | 1 | 0% | 1,656 | 1,666 | +1% | 0 | 0 | — |
▸case-02 To make a navigation sidebar slide animation feel smoother, a developer animates the CSS layout property `left` from `-300px` to `0px`. Users report visual jank during sliding. Which CSS property should be animated instead to run on the compositor thread? | pass→pass | 4,791 | 4,638 | -3% | 1 | 1 | 0% | 771 | 870 | +13% | 0 | 0 | — |
▸case-03 When a user clicks a 'Like' button on a post, an engineer proposes showing a loading spinner overlay for 500ms before filling the heart icon to wait for the backend database write. What visual response time threshold should the interface achieve for actions to feel instantaneous? | pass→pass | 5,455 | 7,527 | +38% | 1 | 1 | 0% | 1,005 | 1,377 | +37% | 0 | 0 | — |
▸case-04 During initial page load on our news portal, late-loading banner ads shift body text down dynamically. The dev lead claims a Cumulative Layout Shift (CLS) score of 0.4 is acceptable as long as main content loads quickly. What maximum CLS threshold should the team enforce for visual layout stability? | pass→pass | 6,248 | 8,967 | +44% | 1 | 1 | 0% | 1,090 | 1,414 | +30% | 0 | 0 | — |
▸case-05 Users experience scroll jank on mobile web browsers when dragging through our product gallery. The event handler binds touch events using standard `addEventListener('touchmove', handler)`. How should the event listener registration options be updated to prevent main-thread scroll blocking? | pass→pass | 7,589 | 7,524 | -1% | 1 | 1 | 0% | 1,325 | 1,378 | +4% | 0 | 0 | — |
▸case-06 Our marketing landing page features full-screen parallax zoom and continuous rotation animations. Some users experience motion sensitivity. How should team styles handle user operating system accessibility settings for motion? | pass→pass | 13,293 | 16,243 | +22% | 1 | 1 | 0% | 2,509 | 2,533 | +1% | 0 | 0 | — |
▸case-07 Core Web Vitals tracking reveals an Interaction to Next Paint (INP) latency of 450ms when opening interactive multi-select drop-downs. The front-end engineer believes 450ms is standard for complex web apps. What maximum INP threshold should be targeted for responsive interaction? | pass→pass | 6,225 | 9,503 | +53% | 1 | 1 | 0% | 1,094 | 1,780 | +63% | 0 | 0 | — |
▸case-08 A long vertical feed containing 200 detailed card components suffers frame drops during scrolling on mobile devices. A developer suggests using custom JavaScript scroll listeners to set `display: none` on offscreen cards. Which modern CSS property natively defers rendering of offscreen elements? | pass→pass | 5,510 | 3,621 | -34% | 1 | 1 | 0% | 691 | 628 | -9% | 0 | 0 | — |
▸case-09 When reordering elements in a photo grid, inserting items causes surrounding cards to snap instantly into place without motion. The dev proposes reading `getBoundingClientRect()` on every animation frame to calculate positions. Which standard performance animation technique should the team adopt? | fail→fail | 7,059 | 7,237 | +3% | 1 | 1 | 0% | 1,169 | 1,276 | +9% | 0 | 0 | — |
▸case-10 On slow mobile connections, custom web typography takes 2 seconds to load, leaving headlines invisible (Flash of Invisible Text). The designer prefers keeping text invisible until custom fonts download. How should font loading be configured in CSS to prioritize readability? | pass→pass | 10,940 | 9,266 | -15% | 1 | 1 | 0% | 2,117 | 1,893 | -11% | 0 | 0 | — |
▸case-11 In our task management application, marking a task complete waits for a 400ms server network response before showing the checked state icon. The visual feel feels sluggish. How should user action state changes be updated before server confirmation? | pass→pass | 14,088 | 12,937 | -8% | 1 | 1 | 0% | 2,155 | 2,082 | -3% | 0 | 0 | — |
▸case-12 A visual designer recommends setting button hover state transitions to 800ms for a luxurious cinematic feel. How should micro-interaction animation durations for UI controls be bounded so they do not feel sluggish? | pass→pass | 13,143 | 14,063 | +7% | 1 | 1 | 0% | 2,329 | 2,436 | +5% | 0 | 0 | — |
▸case-13 A analytics card takes 1.5 seconds to fetch initial data and currently displays a small centered spinner icon. To lower perceived waiting time and reduce layout shifts upon load, what visual placeholder strategy should be implemented? | pass→pass | 10,486 | 8,980 | -14% | 1 | 1 | 0% | 1,774 | 1,516 | -15% | 0 | 0 | — |
▸case-14 In an e-commerce search field, every typed character fires a network request immediately, resulting in out-of-order response flickers. A developer proposes removing live search and requiring users to click a submit button. How should input event execution be handled to retain live feel efficiently? | pass→pass | 13,609 | 13,496 | -1% | 1 | 1 | 0% | 2,168 | 2,132 | -2% | 0 | 0 | — |
▸case-15 A client-side data parsing function runs in a single loop for 180ms, freezing button press interactions on the page. The developer wants to prevent browser main-thread locking without rewriting the code into web workers. How should long execution tasks yield control back to the browser? | pass→pass | 10,645 | 12,851 | +21% | 1 | 1 | 0% | 2,146 | 2,037 | -5% | 0 | 0 | — |
▸case-16 An interactive data table creates 2,000 active DOM elements at once, causing heavy memory consumption and scroll stuttering. The lead developer wants to add `will-change: transform` to all 2,000 row nodes. What rendering optimization technique should be used for large datasets? | fail→fail | 7,013 | 7,257 | +3% | 1 | 1 | 0% | 1,346 | 1,288 | -4% | 0 | 0 | — |
▸case-17 For a swipeable sheet UI component, the mobile team applies a fixed 400ms linear CSS transition when released, causing abrupt unnatural stops when swiped at high velocity. How should gesture-driven snap animations be configured for natural feel? | pass→pass | 15,158 | 13,808 | -9% | 1 | 1 | 0% | 2,278 | 2,484 | +9% | 0 | 0 | — |
▸case-18 Users complain that tapping navigation icons on mobile web feels laggy because highlighting only activates after the native touch tap delay fires the `click` event. How should active state visual feedback be triggered for touch inputs? | pass→pass | 12,382 | 13,334 | +8% | 1 | 1 | 0% | 2,321 | 2,445 | +5% | 0 | 0 | — |
▸case-19 Scrolling through an image-heavy photo feed causes micro-stutters whenever high-resolution PNGs complete downloading and decode synchronously on the main thread. Which HTML attribute handles image decoding off the main thread? | pass→pass | 2,846 | 3,093 | +9% | 1 | 1 | 0% | 455 | 505 | +11% | 0 | 0 | — |
▸case-20 Our PostgreSQL database server CPU usage spikes during peak traffic due to slow execution on queries filtering the `orders` table by `customer_id` and `created_at`. How should the database index be structured to speed up query execution? | pass→pass | 11,668 | 9,396 | -19% | 1 | 1 | 0% | 2,282 | 1,852 | -19% | 0 | 0 | — |
▸case-21 The infrastructure team needs to update Nginx configuration files to disable legacy SSL protocols and enable secure TLS 1.2 and 1.3 ciphers. Which Nginx configuration directive sets the active protocols? | pass→pass | 3,493 | 2,252 | -36% | 1 | 1 | 0% | 678 | 442 | -35% | 0 | 0 | — |
▸case-22 A graphic designer is creating a custom icon collection in Figma and needs to export them for crisp, scale-independent rendering across various screen densities without pixelation. Which file format should be exported? | pass→pass | 4,598 | 4,981 | +8% | 1 | 1 | 0% | 616 | 881 | +43% | 0 | 0 | — |