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Feature: Back-to-Top Button

Purpose​

  • Feature name: Back-to-top button
  • Why this feature exists: Help reviewers navigate long pages without losing context.

Scope​

In scope​

  • visibility toggle based on scroll position
  • smooth scroll behavior with reduced-motion fallback

Out of scope​

  • global navigation links
  • theme switching

Prereqs / Inputs​

  • client-side JavaScript enabled
  • reduced-motion preferences respected by browser

Procedure / Content​

Feature summary​

  • Feature name: Back-to-top button
  • Feature group: Navigation and UX polish
  • Technical summary: Uses an Intersection Observer sentinel and smooth scrolling for return-to-top behavior.
  • Low-tech summary: A button appears after scrolling to quickly return to the top.

Feature in action​

  • Where to see it working: Any long page such as /projects.

Confirmation Process​

Manual​

  • Steps: Scroll down past the fold, click the back-to-top button.
  • What to look for: Button appears after scrolling, page scrolls to top, reduced-motion users get instant jump.
  • Artifacts or reports to inspect: None.

Tests​

Potential behavior if broken or misconfigured​

  • Button never appears due to missing sentinel.
  • Scroll behavior ignores reduced-motion preferences.

Long-term maintenance notes​

  • Re-verify behavior after layout changes that shift scroll length.

Dependencies, libraries, tools​

  • Next.js App Router
  • React
  • Tailwind CSS

Source code references (GitHub URLs)​

ADRs​

  • None.

Runbooks​

  • None.

Additional internal references​

Validation / Expected outcomes​

  • Button appears after scrolling and returns the user to the top.

Failure modes / Troubleshooting​

  • Button not visible: check sentinel placement and CSS.
  • Scroll jumps inconsistently: verify reduced-motion handling.

References​

  • None.