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Underline Follow

A glowing emerald-to-tan gradient underline slides and resizes to follow hovered nav links; wanders until first deliberate input across links when unhovered.

csslight complexitysubtle motionhover

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When to use it

Portfolio or app nav bars needing a polished active-state indicator with ambient motion between interactions.

When not to

Nav bars with more than 6 items where the idle wander may feel restless; or any context requiring a truly static nav indicator. Autonomous preview ends at first deliberate input and never resumes.

Working with an AI agent

Every component ships agent-ready metadata. An example instruction for this one:

Change the underline gradient to gold-to-orange by setting --accent-iris:#f59e0b and --accent-cyan:#f97316, and slow the idle cycle to 2400ms. Theme: dark tokens live in :root, the light variant in :root[data-theme="light"]; ?theme=light or a {type:'forever:theme'} postMessage switches at runtime. Autonomous preview ends at first deliberate input and never resumes.

Safe to edit

  • accent colors (--accent-iris, --accent-cyan)
  • transition duration (420ms on .c06-nav__ink)
  • idle wander interval (1600ms in setTimeout) Autonomous preview ends at first deliberate input and never resumes.
  • underline height (height:2px on .c06-nav__ink)
  • gap between nav items (gap:6px)
  • theme tokens (:root dark defaults + [data-theme=light] overrides)

Keep intact

  • prefers-reduced-motion guard (kills idle loop)
  • visibilitychange stop/loop guard
  • IIFE wrapper
  • mouseleave return-to-active logic
  • theme hook (?theme= bootstrap + forever:theme message listener + theme tokens)
  • demo-v1 preview lifecycle: initialize demoEnabled from window.__foreverPreview and stop attract work on the window forever:interactive event; retain manual feedback, settling, cleanup and explicit sessions

Known limitations

  • Idle wander uses offsetLeft/offsetWidth — breaks if nav is not laid out when loop starts Autonomous preview ends at first deliberate input and never resumes.
  • No touch equivalent for hover; on mobile the underline stays on last-active item only
  • Autonomous idle cycle must be removed or paused for production click-driven nav Autonomous preview ends at first deliberate input and never resumes.
  • State remains local to each mounted instance; format/theme remount preserves takeover, not component values.

navigationunderlinehovergradientindicatorui-controlidle-wander

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