A section-by-section composition can separate content into scenes, but the visitor still needs to know where they are and how to reach another section. Fixed numbers after omissions and content clipped to viewport height can put movement at odds with reading. I review the presentation effect alongside the wayfinding function.

An earlier restyling task required preserving its original full-page movement, slider and reveal effects. The current replacement adapter maps surviving sections to original indexes and redirects a missing target toward a later survivor. Here I explain that principle and implement a separate new menu example. It does not claim to recreate every behavior of the original screen.

Distinguish a preserved system from a new example

Replacing an entire scrolling engine in a task that preserves an existing composition is a larger change than substituting colors or material. The inspected handoff explicitly preserves layout, full-page movement, sliders and reveal effects. The replacement template also defines boundaries for preserving original geometry, timing and behavior.

The code below is a small implementation written for this article, not a patch to the original engine. It connects sections and a menu within a separate scroll region. Applying the idea to an existing site requires an adapter compatible with its preserved behavior and movement API. A useful new example is not authorization to change that contract.

Section numbers must still mean the correct destination

After material is omitted, the second current section may no longer be the second original section. The inspected adapter reads actual section IDs to recover original order. When a requested original target is missing, it selects a later surviving target. This helps keep the original effect from being assigned to a different section.

The new example navigates by surviving ID rather than a fixed number. A button for an absent item is hidden, and the currently read section is indicated. That is distinct from restoring every original effect. The small ID connection and the preserved engine’s timing and index mapping need separate review.

Represent current location beyond color alone

When a menu disappears beyond the viewport, finding another destination may require traversing several sections again. This example keeps the menu outside its scrolling region and adds aria-current to the active item. Background and underline also change. That records the meaning of current location beyond a color-only decoration.

A reading line within the region and section geometry determine the current item. A long section retains its identity while it crosses that line, and an omitted ID is absent from the calculation. The selected line ratio belongs to this example; it is not a universal setting. Review it against the actual menu and section lengths.

Content can exceed the height of one scene

Making a scene resemble one screen is different from hiding content outside a fixed height. The example sets a minimum height while allowing actual height to grow. On small screens it removes that minimum and snapping. Content and the onward route should not disappear when the screen becomes smaller.

Reduced-motion preference disables smooth movement and snapping in this implementation. Wheel and touch input are not intercepted to force an exclusive movement system. These conditions are code facts rather than a verification across devices. Zoom, keyboard use and reaching the end of long content still require rendered review.

Implementation and its supporting styles

JavaScript reads surviving section geometry and updates the current menu item. Activating a button moves to its section ID and focuses the heading. If focus is on a newly absent button, it moves to the scroll region. The cleanup function removes events and observation so the attachment has a defined lifecycle.

The module does not intercept every keyboard input. It uses native button activation and region scrolling. The CSS applies to the example’s section and menu classes. A real site with a fixed header, nested scrolling or an existing full-page library needs its target and offset reviewed for that environment.

Explore the implementation

JavaScript · Location guidance for surviving sections

export function currentReadingSection(rects,viewport){
 if(!Array.isArray(rects)||!Number.isFinite(viewport?.top)||!Number.isFinite(viewport?.bottom)||viewport.bottom<=viewport.top)throw new TypeError('Finite viewport bounds required');
 const visible=rects.filter(x=>typeof x.id==='string'&&Number.isFinite(x.top)&&Number.isFinite(x.bottom)&&x.bottom>x.top&&x.bottom>viewport.top&&x.top<viewport.bottom);
 if(!visible.length)return null;
 const line=viewport.top+(viewport.bottom-viewport.top)*0.3;
 return visible.find(x=>x.top<=line&&x.bottom>line)?.id||visible.reduce((best,x)=>Math.abs(x.top-line)<Math.abs(best.top-line)?x:best).id;
}
export function attachSectionGuide(scroller,menu){
 const win=scroller.ownerDocument.defaultView;let frame=0,closed=false;
 const sections=()=>Array.from(scroller.querySelectorAll('[data-guide-section]'));
 const buttons=()=>Array.from(menu.querySelectorAll('button[data-section]'));
 function refresh(){
  if(closed)return;const items=sections(),ids=new Set(items.map(x=>x.id));
  const root=scroller.getBoundingClientRect();
  const current=currentReadingSection(items.map(x=>({id:x.id,...bounds(x)})),root);
  const active=scroller.ownerDocument.activeElement;
  for(const button of buttons()){
   const hidden=!ids.has(button.dataset.section);if(hidden&&button===active)scroller.focus({preventScroll:true});
   button.hidden=hidden;
   if(!hidden&&button.dataset.section===current)button.setAttribute('aria-current','location');else button.removeAttribute('aria-current');
  }
  menu.hidden=!ids.size;
 }
 function bounds(element){const r=element.getBoundingClientRect();return {top:r.top,bottom:r.bottom};}
 function queue(){if(!closed){win.cancelAnimationFrame(frame);frame=win.requestAnimationFrame(refresh);}}
 function navigate(event){
  const button=event.target.closest('button[data-section]');if(!button||!menu.contains(button))return;
  const target=sections().find(x=>x.id===button.dataset.section);if(!target)return;
  const top=target.getBoundingClientRect().top-scroller.getBoundingClientRect().top+scroller.scrollTop-scroller.clientTop;
  scroller.scrollTo({top:Math.max(0,top),behavior:win.matchMedia?.('(prefers-reduced-motion: reduce)').matches?'auto':'smooth'});
  const heading=target.querySelector('h2,h3');if(heading){heading.setAttribute('tabindex','-1');heading.focus({preventScroll:true});}
 }
 scroller.addEventListener('scroll',queue,{passive:true});menu.addEventListener('click',navigate);win.addEventListener('resize',queue);
 const observer=win.MutationObserver?new win.MutationObserver(queue):null;
 observer?.observe(scroller,{childList:true,subtree:true});refresh();
 return {refresh,destroy(){closed=true;win.cancelAnimationFrame(frame);observer?.disconnect();scroller.removeEventListener('scroll',queue);menu.removeEventListener('click',navigate);win.removeEventListener('resize',queue);}};
}

An executable example with a long detail section

The example includes an opening, a long detail section and a closing section, with one synthetic item omitted. The menu and scrolling region are separate, and the location function is included in the executable HTML block. Original business identities and imagery are not transferred.

Publication checks inspect the public execution frame and code. Rendered scrolling and focus movement in this new frame remain unverified while existing Studio Chrome work is preserved. Implementation, public response and observed browser behavior are recorded as different verification scopes.

Explore the implementation

CSS · Growing sections and their menu

.guide-scroller { max-block-size: 65svh; overflow-y: auto; scroll-snap-type: y proximity; scroll-behavior: auto; border: 1px solid #b9c8be; }
.guide-section { min-block-size: 60svh; block-size: auto; padding: clamp(20px, 4vw, 48px); scroll-snap-align: start; scroll-margin-block-start: 12px; }
.guide-section + .guide-section { border-block-start: 1px solid #b9c8be; }
.guide-menu { display: flex; flex-wrap: wrap; gap: 8px; margin-block: 16px; }
.guide-menu button { padding: 10px 14px; font: inherit; color: #263b30; background: #fff; border: 1px solid #8aa494; cursor: pointer; }
.guide-menu button[aria-current] { background: #263b30; color: #fff; text-decoration: underline; }
.guide-scroller:focus-visible, .guide-menu button:focus-visible { outline: 3px solid #326c4d; outline-offset: 3px; }
@media (max-width: 520px) { .guide-section { min-block-size: auto; } .guide-scroller { scroll-snap-type: none; } }
@media (prefers-reduced-motion: reduce) { .guide-scroller { scroll-snap-type: none; } }

Code checks and review before application

Nine checks used synthetic geometry and fake DOM events: initial and later sections, long-section identity, gaps, absent sections, invalid viewport bounds, hidden-button focus replacement, ID navigation offsets and heading focus, reduced motion, and listener cleanup. These results establish the function and connection code under those conditions.

No original template files were changed. Actual full-page animation, cross-browser CSS support and keyboard or touch experience were not tested. Before application, check destinations, reachability of final content, zoom and small-screen movement. This module leaves a wayfinding function alongside the effect used to present each scene.