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.

Desktop Principles

Desktop UX context. Loaded when desktop is detected (macOS, Windows, Linux desktop, web desktop). Concise rules here. Deep-dive in references/.

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Hover States Are Mandatory

Hover is the primary affordance signal on desktop, the inverse of mobile. A pointer hovering over a target without immediate visual feedback feels broken: users rely on :hover to confirm an element is interactive before committing to a click. Every clickable surface must have a distinct hover style, ideally with a 100-200ms transition so the change is perceptible without feeling sluggish.

CSS - hover styles for interactive elements:

.button {
  background: var(--surface);
  transition: background 120ms ease-out, transform 120ms ease-out;
}

.button:hover {
  background: var(--surface-hover);
  transform: translateY(-1px);
}

.button:active {
  transform: translateY(0);
}

SwiftUI - .onHover is the portable hover signal; .hoverEffect is iOS/iPadOS-only and must be #if-gated:

Modifier	Availability	Notes
.onHover { Bool }	iOS 13.4+, iPadOS 13.4+, Mac Catalyst 13.4+, macOS 10.15+, visionOS 1.0+	the one that works on macOS
.onContinuousHover { HoverPhase }	iOS 17.0+, macOS 14.0+, tvOS 17.0+, visionOS 1.0+	pointer position, not just in/out
.hoverEffect(_:)	iOS 13.4+, iPadOS 13.4+, Mac Catalyst 13.4+, tvOS 16.0+, visionOS 1.0+ - macOS unavailable	compile error in a macOS target
.pointerStyle(_:)	macOS 15.0+, visionOS 2.0+	change the macOS cursor over a view

struct ToolbarButton: View {
  @State private var hovering = false