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Mobile-specific UX principles - touch targets, hover-less doctrine, thumb zones, safe areas, gestures, mobile perf budgets. Cross-platform (web mobile, iOS, Android).
Passed 22 of 24 test cases with the skill, and 17 of 24 without it.
and 3 more in the full report
5 fixed17 passed either way2 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 5 test cases the skill fixed. Same model, same prompt, with and without the skill.
A mobile engineer is profiling smooth scrolling performance in a native list view. On standard 60Hz displays, each frame has approximately 16.67ms. What is the frame execution time budget when targeting high-refresh displays such as iOS ProMotion or 120Hz Android devices?
| Checked | Without skill | With skill |
|---|---|---|
| Sets maximum frame budget to 8.33 milliseconds for 120Hz high-refresh screens | Passed | Passed |
| Warns that main thread work exceeding the budget causes frame drops | Missed | Passed |
The instructions your model reads when the skill loads.
Version-sensitive. Every API name, SDK gate and browser-support claim below was verified on 2026-09-08 against primary sources. What against, and when, is in
_jutsu/VERSIONS.md. If that date is old, re-verify before acting on a version number.
Touch-first UX context. Loaded when mobile is detected (web mobile, iOS, Android). Concise rules here. Deep-dive in
references/.
| Platform | Recommended (design to this) | Hard floor | Spacing | Spec |
|---|---|---|---|---|
| Apple iOS / iPadOS | 44x44 pt | 28x28 pt | ~12 pt padding around bezeled controls, ~24 pt around unbezeled ones | Apple HIG, Accessibility > Mobility |
| Apple watchOS | 44x44 pt | 28x28 pt | as above | Apple HIG |
| Android | 48x48 dp | 48x48 dp | 8 dp between targets | Material Design 3 |
| Web mobile | 44x44 CSS px | 24x24 CSS px | 24 px un-overlapped spacing satisfies the AA exception | WCAG 2.5.5 Target Size (Enhanced), AAA = 44x44; WCAG 2.5.8 Target Size (Minimum), AA = 24x24 |
Rule of thumb: any tap target smaller than the platform minimum is a usability bug, period.
The hit area can extend beyond the visible glyph (use padding, hitSlop, or a transparent inner spacer), but the interactive surface must reach the minimum. Spacing matters as much as size: two 44pt buttons touching edges are still mistappable.
:hover does not exist on touch. Treating it as a primary trigger means hidden affordances on every phone. Anything reachable only by hover is, on mobile, simply gone. Visible-by-default is the rule; hover styles are a desktop enhancement, never a load-bearing interaction.
CSS - gate hover styles behind a media query:
.card { opacity: 1; transform: translateY(0); }
@media (hover: hover) and (pointer: fine) {
.card { opacity: 0.85; }
.card:hover { opacity: 1; transform: translateY(-2px); }
}
SwiftUI - tap and long-press, no pseudo-hover:
test cases passed, vs 17 / 24 without
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