▸case-01 We are building a like button for a post card in a React web application. Currently, clicking the button triggers an async API call to update the database and only updates the heart icon state when the API response returns successfully (150ms-500ms latency). Users complain the button feels sluggish. How should we handle the state update and potential server error to make the interface feel instantaneous? | pass→pass | 12,806 | 14,181 | +11% | 1 | 1 | 0% | 2,494 | 2,976 | +19% | 0 | 0 | — |
▸case-02 A modal window on our Web application pops open instantly without transition, feeling jarring to users. We want to add a CSS transition for entering and exiting. Should entering elements use ease-in or ease-out curve, and what duration range (in milliseconds) is recommended for standard UI micro-interactions like dialog transitions? | pass→pass | 9,751 | 8,976 | -8% | 1 | 1 | 0% | 1,907 | 1,840 | -4% | 0 | 0 | — |
▸case-03 Our mobile web app navigation toolbar has several small icon buttons styled with 24x24px dimensions. Mobile users report frequently tapping the wrong button or missing taps entirely. What minimum target area dimension should be applied to touch controls according to accessibility and mobile UI design guidelines? | pass→pass | 10,300 | 7,577 | -26% | 1 | 1 | 0% | 2,192 | 1,630 | -26% | 0 | 0 | — |
▸case-04 We added scale and slide animations to all page section reveals on scroll. However, users sensitive to visual motion report feeling motion sickness. How should CSS media queries be used to respect user system preferences for motion? | pass→pass | 8,516 | 9,852 | +16% | 1 | 1 | 0% | 1,699 | 2,082 | +23% | 0 | 0 | — |
▸case-05 An inline search field sends a GraphQL search request on every single keypress event, causing network congestion and flickering UI search results as responses return out of order. What technique and timing parameter should be applied to user keystroke input before triggering the network call? | fail→pass | 5,924 | 5,061 | -15% | 1 | 1 | 0% | 1,031 | 949 | -8% | 0 | 0 | — |
▸case-06 When lazy-loaded images render into a news feed container, the surrounding content abruptly shifts downward, causing high Cumulative Layout Shift (CLS). How should image container CSS styles be defined prior to the image loading to prevent this layout jump? | pass→pass | 11,486 | 10,525 | -8% | 1 | 1 | 0% | 2,319 | 2,284 | -2% | 0 | 0 | — |
▸case-07 Users clicking primary action buttons in our web app report that buttons feel static because there is no visual indication when the physical mouse button or screen touch is pressed down prior to release. How should CSS pseudo-classes provide immediate tactile press feedback? | pass→pass | 12,436 | 10,912 | -12% | 1 | 1 | 0% | 2,536 | 2,303 | -9% | 0 | 0 | — |
▸case-08 When a user navigates to their user dashboard, the page remains completely blank for 1.2 seconds until data arrives, at which point content pops into view. Should we replace this with a single full-page centered spinner or layout skeleton placeholders, and why? | pass→pass | 9,286 | 7,427 | -20% | 1 | 1 | 0% | 1,615 | 1,394 | -14% | 0 | 0 | — |
▸case-09 A design update applied `outline: none` across all global CSS selectors to eliminate the blue focus rectangle around clicked buttons. Keyboard accessibility users can no longer determine which element has focus. How should focus styling be configured so outline rings only appear during keyboard navigation? | pass→pass | 7,864 | 7,558 | -4% | 1 | 1 | 0% | 1,542 | 1,484 | -4% | 0 | 0 | — |
▸case-10 On iOS Safari mobile web browsers, users experience a noticeable 300ms delay between tapping a custom interactive button element and the click handler firing. What CSS property should be applied to disable double-tap zooming behavior and eliminate this tap delay? | pass→pass | 3,553 | 3,419 | -4% | 1 | 1 | 0% | 557 | 684 | +23% | 0 | 0 | — |
▸case-11 Our registration form displays immediate red error messages for 'invalid email format' as soon as the user types their first character into the email field, causing user frustration. At what point during user interaction should inline field validation error messages first be triggered? | pass→pass | 10,912 | 10,143 | -7% | 1 | 1 | 0% | 1,744 | 1,734 | -1% | 0 | 0 | — |
▸case-12 A primary form submit button uses the standard HTML `disabled` attribute while form fields are incomplete. As a result, screen reader and keyboard users cannot focus or inspect the submit button to understand why submission is unavailable. How should button state and focusability be structured instead? | pass→pass | 11,017 | 11,767 | +7% | 1 | 1 | 0% | 2,101 | 2,384 | +13% | 0 | 0 | — |
▸case-13 Our application displays transient notification toasts in the corner when background async operations succeed or fail. What auto-dismiss duration and persistence rule should be applied for informative success messages versus critical error messages requiring user intervention? | fail→fail | 12,246 | 10,467 | -15% | 1 | 1 | 0% | 2,179 | 1,973 | -9% | 0 | 0 | — |
▸case-14 On mobile devices, tapping a card item triggers CSS `:hover` styles that remain stuck on screen even after navigation or scroll. How can media queries prevent hover styles from persisting on touchscreen devices? | pass→pass | 8,664 | 7,828 | -10% | 1 | 1 | 0% | 1,724 | 1,571 | -9% | 0 | 0 | — |
▸case-15 A web-based mobile task checklist application wants to provide subtle physical sensory feedback when a user checks off a task item. What standard browser API can trigger brief vibration feedback on supported mobile hardware? | pass→pass | 4,370 | 3,722 | -15% | 1 | 1 | 0% | 748 | 679 | -9% | 0 | 0 | — |
▸case-16 When closing a slide-out drawer or modal overlay, using a slow transition makes the interface feel sluggish. What motion easing curve and relative speed should be used for exit transitions compared to enter transitions? | pass→pass | 9,122 | 7,385 | -19% | 1 | 1 | 0% | 1,787 | 1,406 | -21% | 0 | 0 | — |
▸case-17 In a drag-and-drop list reordering interface, users feel uncertain where a dragged item will land when released. What visual micro-interactions and layout placeholders should be provided during the drag gesture? | pass→pass | 14,575 | 12,679 | -13% | 1 | 1 | 0% | 2,329 | 2,222 | -5% | 0 | 0 | — |
▸case-18 When a user views an empty 'Saved Items' page, the screen simply displays text reading 'No items found.' How should empty state views be designed to improve user engagement and guidance? | pass→pass | 8,799 | 10,420 | +18% | 1 | 1 | 0% | 1,741 | 1,934 | +11% | 0 | 0 | — |
▸case-19 When loading custom web fonts on slow connections, pages display blank unreadable text until font files finish downloading, causing a Flash of Invisible Text. Which CSS `@font-face` descriptor resolves this by displaying fallback system fonts immediately? | pass→pass | 3,966 | 3,791 | -4% | 1 | 1 | 0% | 697 | 797 | +14% | 0 | 0 | — |
▸case-20 Our PostgreSQL database query `SELECT * FROM orders WHERE user_id = $1 ORDER BY created_at DESC LIMIT 20` is taking 800ms on a table with 10 million records. How should we optimize database indexing for this query? | pass→pass | 11,629 | 10,477 | -10% | 1 | 1 | 0% | 2,175 | 2,055 | -6% | 0 | 0 | — |
▸case-21 How should an API backend architecture securely implement JSON Web Token (JWT) rotation using short-lived access tokens and refresh tokens? | pass→pass | 18,846 | 17,906 | -5% | 1 | 1 | 0% | 3,605 | 3,366 | -7% | 0 | 0 | — |
▸case-22 In a 3D WebGL Fragment Shader written in GLSL, how is Phong specular highlight calculated using normal vectors, light direction, and view direction? | pass→pass | 11,944 | 11,942 | -0% | 1 | 1 | 0% | 2,442 | 2,573 | +5% | 0 | 0 | — |