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.

Mobile Principles

Touch-first UX context. Loaded when mobile is detected (web mobile, iOS, Android). Concise rules here. Deep-dive in references/.

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Touch Targets

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.

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No-Hover Doctrine

: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); }
}