WAI-ARIA Implementation with Pure CSS Architecture
==================================================

Here's how the codebase implements key WAI-ARIA specifications using
entirely CSS and semantic HTML, with no JavaScript dependencies:

1. **Semantic HTML Foundation**
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* **Uses native form controls** (``<input type="radio">``) that have built-in accessibility
* **Fieldset/Legend structure** provides semantic grouping that screen readers understand natively
* **Pure CSS tab switching** via ``:checked`` pseudo-class and sibling selectors
* **No JavaScript required** for any core functionality

2. **ARIA Roles (Semantic Clarity)**
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* ``role="radiogroup"`` on fieldset - accurately describes the selection mechanism
* ``role="tabpanel"`` on content panels - correctly identifies them as switchable content views
* ``role="region"`` on container - establishes it as a landmark for easy navigation
* **CSS-only benefit**: These roles are static HTML attributes that work universally

3. **ARIA Relationships (Connected Experience)**
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* ``aria-labelledby`` links panels to their controlling radios
* ``aria-controls`` connects radios to their corresponding panels for screen reader sync
* ``aria-describedby`` connects radios to hidden descriptive text
* Container's ``aria-labelledby`` points to the visible legend
* **CSS-only benefit**: All relationships defined in HTML, completely static and reliable

4. **Keyboard Navigation (Native Browser Behavior)**
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* Uses **native radio button keyboard behavior** exclusively:

  * Tab enters/exits the group
  * Arrow keys navigate AND select (handled entirely by browser)
  * Enter/Space activate selections (native browser behavior)

* **CSS-only benefit**: Works through browser's built-in form control behavior with zero custom code

5. **Screen Reader Announcements**
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* Visible, meaningful legend announces the choice context
* Hidden descriptions (``sr-only``) provide additional context per option
* Standard radio group announcements work through HTML structure alone
* **CSS-only benefit**: Announcements work through semantic HTML without any scripting

6. **Focus Management**
-----------------------
* ``tabindex="0"`` on panels makes them focusable after tab selection
* Visual focus indicators via CSS ``:focus`` pseudo-class
* Browser handles all focus transitions using standard form behavior
* **CSS-only benefit**: Focus management works without any custom JavaScript

7. **Pure CSS Architecture Strategy**
-------------------------------------
.. code-block:: text

   Implementation Layer (HTML/CSS only):
   - Complete tab switching functionality
   - Native keyboard navigation
   - Full screen reader support
   - Cross-browser compatibility
   - No JavaScript dependencies

   Benefits:
   - Maximum compatibility (works everywhere CSS works)
   - Better performance (no JS parsing/execution)
   - Enhanced security (no script execution)
   - Simplified maintenance (fewer moving parts)

8. **Universal Compatibility**
------------------------------
* **Without CSS**: Content displays linearly with functional radio buttons
* **With CSS disabled**: All content remains accessible in logical order
* **JavaScript disabled**: Full functionality maintained (since none is used)
* **Restrictive environments**: Works with strict Content Security Policies
* **Non-HTML output** (LaTeX/PDF): Renders as readable sequential content

Design Philosophy
=================

This implementation prioritizes **robustness and universality** over complex
interactive patterns. The conscious design choice to use **radiogroup semantics**
for tab-like behavior achieves:

#. **Maximum reliability** through standard form controls
#. **Universal compatibility** across all browsers and assistive technologies
#. **Zero dependencies** on JavaScript or complex CSS features
#. **Predictable behavior** that users already understand

The result is an accessible component that:

* Works in every environment where HTML and CSS are supported
* Provides consistent behavior across all platforms and assistive technologies
* Requires no fallbacks or compatibility shims
* Maintains perfect accessibility through semantic HTML structure
* Offers better performance than JavaScript-dependent alternatives

Technical Implementation Details
================================

**CSS Selector Strategy**: Uses ``data-tab-index`` attributes with CSS
``[data-tab-index="N"]:checked`` selectors to show/hide panels, avoiding
fragile nth-child calculations.

**Keyboard Navigation**: Leverages browser's native radiogroup keyboard
handling, which already implements the correct ARIA patterns for grouped
selection controls.

**Screen Reader Compatibility**: Relies on standard form semantics that
all screen readers support consistently, rather than custom ARIA state
management.

**Focus Indicators**: Uses CSS ``:focus`` and ``:focus-within`` to provide
clear visual feedback without requiring focus event handling.

This architecture demonstrates that **accessible design often benefits from
simplicity** rather than complexity, achieving better compatibility through
standard web technologies rather than custom implementations.