====== Shadows: Rule 3 - The "1% Alpha" Workaround ======

To create a completely transparent, hollow shape that successfully displays a solid border and casts a shadow, the rendering engine's binary logic must be tricked. Under normal conditions, absolute transparency (0% Alpha) causes the engine to skip shadow calculations entirely.

===== The Technical Fix ===== 
  * **The Action:** - Set the shape's Alpha Fill opacity for Color 1 and Color 2 to ''01'', resulting in **''ARGB 01000000''** (black) or **''ARGB 01FFFFFF''** (white).
  * **Border Requirement:** - A border width of at least ''3'' or ''5'' is required. A width of ''1'' may be mathematically clipped away by anti-aliasing on high-resolution screens.
  * **Resulting Effect:** - **A hollow ring shadow** that mirrors the border outline is cast rather than a solid dark circle.

===== Why This Happens =====
The ''01'' value represents approximately 0.4% opacity. To the human eye, the center remains completely transparent. Mathematically, however, the engine recognizes a >0% fill, which forces the calculation of the object's border and shadow. Because the fill is only 1% opaque, its specific shadow is functionally invisible, leaving only the shadow cast by the fully opaque border.

===== Technical Proof: Test 5 =====
The following results from the controlled Test Matrix prove that Test 5 is the only configuration that bypasses the "Zero-Alpha" limitation to produce a hollow shadow.

{{tablelayout?colwidth="600px,150px"&rowsHeaderSource=auto&float=center}}
^  Rendering Matrix (The Cause)  ^  Visual Results (The Effect)  ^
| \\ \\ \\ {{:section:section-shadow_test_parameters.webp?direct&550}} | {{:section:section-shadow_controlled_tests_1_-_7.webp?direct&150}} |

  * **Test 5 (The Success):** - Demonstrates that the micro-opacity successfully forces the shadow to render behind an effectively invisible fill[cite:.
  * **Tests 2, 3, & 4 (The Failures):** - Confirm that absolute 0% Alpha Fill results in no shadow calculation, regardless of border thickness.

===== Practical Comparison =====
The success of Rule 3 is highly dependent on background contrast. 

^ **Success: White Ring on Blue** ↔️  **Failure: Dark Frame on Dark Blue** ^
|  {{:section:section-shadow-rule5-trumps_rule3.webp?direct&400}}  |  

|  High luminance separation ...\\ the hollow shadow clearly visible.  |  Low luminance shadow "sinks"\\ into the background (The Contrast Wall).  |
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