Update README and code to set default sparkle shape to 'none' and add opacity control

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/src/shiny_widget.dart

@@ -6,22 +6,45 @@ import 'package:flutter/scheduler.dart';
 
 import 'shiny_controller.dart';
 
+/// Available holographic material profiles rendered by the fragment shader.
 enum HolographStyle {
+  /// Smooth silver foil with soft rainbow flow.
   holographicSilver,
+
+  /// High-contrast crystalline foil with shard-like reflections.
   crackedIce,
+
+  /// Tiled foil with radial diffraction in each tile.
   silverMosaic,
+
+  /// Dense dot-grid gold foil with warm highlights.
   superGoldVinyl,
 }
 
+/// Sparkle silhouette families used by the shader when drawing glints.
 enum SparkleShapeKind {
+  /// Disables sparkle rendering entirely.
+  none,
+
+  /// Star-shaped sparkle with configurable point count and inner radius.
   star,
+
+  /// Rectangular sparkle streak.
   rectangle,
+
+  /// Fixed-side polygon sparkle.
   polygon,
+
+  /// Randomized polygon sparkle per sparkle cell.
   randomPolygon,
+
+  /// Confetti-like elongated rectangle with random rotation.
   confetti,
 }
 
+/// Declarative sparkle shape configuration for [Shiny] and [ShinyCard].
 class SparkleShapeSpec {
+  /// Internal constructor that maps directly to shader uniform values.
   const SparkleShapeSpec._({
     required this.kind,
     required this.primary,
@@ -29,6 +52,15 @@ class SparkleShapeSpec {
     required this.tertiary,
   });
 
+  /// No sparkle output.
+  static const SparkleShapeSpec none = SparkleShapeSpec._(
+    kind: SparkleShapeKind.none,
+    primary: 0.0,
+    secondary: 0.0,
+    tertiary: 0.0,
+  );
+
+  /// Eight-point star sparkle preset.
   static const SparkleShapeSpec eightPointStar = SparkleShapeSpec._(
     kind: SparkleShapeKind.star,
     primary: 8.0,
@@ -36,6 +68,7 @@ class SparkleShapeSpec {
     tertiary: 0.0,
   );
 
+  /// Five-point star sparkle preset.
   static const SparkleShapeSpec fivePointStar = SparkleShapeSpec._(
     kind: SparkleShapeKind.star,
     primary: 5.0,
@@ -43,6 +76,7 @@ class SparkleShapeSpec {
     tertiary: 0.0,
   );
 
+  /// Rectangular sparkle preset.
   static const SparkleShapeSpec rectangle = SparkleShapeSpec._(
     kind: SparkleShapeKind.rectangle,
     primary: 0.24,
@@ -50,6 +84,7 @@ class SparkleShapeSpec {
     tertiary: 1.0,
   );
 
+  /// Diamond sparkle preset.
   static const SparkleShapeSpec diamond = SparkleShapeSpec._(
     kind: SparkleShapeKind.polygon,
     primary: 4.0,
@@ -57,6 +92,7 @@ class SparkleShapeSpec {
     tertiary: 0.78539816339,
   );
 
+  /// Hexagon sparkle preset.
   static const SparkleShapeSpec hexagon = SparkleShapeSpec._(
     kind: SparkleShapeKind.polygon,
     primary: 6.0,
@@ -64,6 +100,7 @@ class SparkleShapeSpec {
     tertiary: 0.0,
   );
 
+  /// Randomized polygon sparkle preset.
   static const SparkleShapeSpec randomPolygon = SparkleShapeSpec._(
     kind: SparkleShapeKind.randomPolygon,
     primary: 0.0,
@@ -71,6 +108,7 @@ class SparkleShapeSpec {
     tertiary: 0.0,
   );
 
+  /// Confetti sparkle preset.
   static const SparkleShapeSpec confetti = SparkleShapeSpec._(
     kind: SparkleShapeKind.confetti,
     primary: 0.34,
@@ -78,6 +116,9 @@ class SparkleShapeSpec {
     tertiary: 1.0,
   );
 
+  /// Creates a custom star sparkle.
+  ///
+  /// [points] is clamped to `[4, 12]` and [innerRatio] to `[0.15, 0.85]`.
   factory SparkleShapeSpec.customStar(
       {int points = 8, double innerRatio = 0.42}) {
     return SparkleShapeSpec._(
@@ -88,6 +129,9 @@ class SparkleShapeSpec {
     );
   }
 
+  /// Creates a custom polygon sparkle.
+  ///
+  /// [sides] is clamped to `[3, 10]` and [aspectRatio] to `[0.4, 2.0]`.
   factory SparkleShapeSpec.customPolygon(
       {int sides = 6, double aspectRatio = 1.0, double rotation = 0.0}) {
     return SparkleShapeSpec._(
@@ -98,6 +142,9 @@ class SparkleShapeSpec {
     );
   }
 
+  /// Creates a custom rectangular sparkle.
+  ///
+  /// Values are clamped to keep shapes visible and numerically stable.
   factory SparkleShapeSpec.customRectangle(
       {double halfWidth = 0.24,
       double halfHeight = 0.055,
@@ -110,6 +157,9 @@ class SparkleShapeSpec {
     );
   }
 
+  /// Creates a custom confetti sparkle.
+  ///
+  /// Values are clamped to keep geometry inside the sparkle cell.
   factory SparkleShapeSpec.customConfetti(
       {double length = 0.34,
       double thickness = 0.045,
@@ -122,13 +172,22 @@ class SparkleShapeSpec {
     );
   }
 
+  /// Sparkle family used by the shader.
   final SparkleShapeKind kind;
+
+  /// Shape parameter 1. Meaning depends on [kind].
   final double primary;
+
+  /// Shape parameter 2. Meaning depends on [kind].
   final double secondary;
+
+  /// Shape parameter 3. Meaning depends on [kind].
   final double tertiary;
 }
 
+/// Applies holographic shader lighting to any child widget.
 class Shiny extends StatefulWidget {
+  /// Creates a shiny wrapper.
   const Shiny({
     super.key,
     required this.child,
@@ -138,22 +197,47 @@ class Shiny extends StatefulWidget {
     this.sparkle = 0.8,
     this.specular = 0.8,
     this.diffraction = 0.8,
-    this.sparkleShape = SparkleShapeSpec.eightPointStar,
+    this.opacity = 1.0,
+    this.sparkleShape = SparkleShapeSpec.none,
     this.style = HolographStyle.crackedIce,
     this.blendMode = BlendMode.screen,
     this.enableShader = true,
   });
 
+  /// Child widget receiving the shader mask.
   final Widget child;
+
+  /// Optional tilt controller stream source.
   final ShinyController? controller;
+
+  /// Explicit tilt override in normalized `[-1.0, 1.0]` space.
   final Offset? tilt;
+
+  /// Color separation strength.
   final double prismatic;
+
+  /// Sparkle strength multiplier.
   final double sparkle;
+
+  /// Main highlight intensity.
   final double specular;
+
+  /// Micro-diffraction intensity.
   final double diffraction;
+
+  /// Global shader opacity multiplier.
+  final double opacity;
+
+  /// Sparkle silhouette specification.
   final SparkleShapeSpec sparkleShape;
+
+  /// Foil style preset.
   final HolographStyle style;
+
+  /// Blend mode applied by [ShaderMask].
   final BlendMode blendMode;
+
+  /// Toggles shader execution.
   final bool enableShader;
 
   @override
@@ -268,7 +352,8 @@ class _ShinyState extends State<Shiny> with TickerProviderStateMixin {
       ..setFloat(10, widget.sparkleShape.kind.index.toDouble())
       ..setFloat(11, widget.sparkleShape.primary)
       ..setFloat(12, widget.sparkleShape.secondary)
-      ..setFloat(13, widget.sparkleShape.tertiary);
+      ..setFloat(13, widget.sparkleShape.tertiary)
+      ..setFloat(14, widget.opacity);
     return shader;
   }
 
@@ -289,6 +374,7 @@ class _ShinyState extends State<Shiny> with TickerProviderStateMixin {
 }
 
 class ShinyCard extends StatefulWidget {
+  /// Creates a card helper that combines clipping, tilt transform, and [Shiny].
   const ShinyCard({
     super.key,
     this.background,
@@ -302,23 +388,52 @@ class ShinyCard extends StatefulWidget {
     this.sparkle = 0.8,
     this.specular = 0.8,
     this.diffraction = 0.8,
-    this.sparkleShape = SparkleShapeSpec.eightPointStar,
+    this.opacity = 1.0,
+    this.sparkleShape = SparkleShapeSpec.none,
     this.style = HolographStyle.crackedIce,
     this.enableShader = true,
   });
 
+  /// Optional card background; defaults to a dark fill.
   final Widget? background;
+
+  /// Optional widget drawn above the shiny background.
   final Widget? foreground;
+
+  /// Card clipping shape.
   final ShapeBorder shape;
+
+  /// Card width.
   final double width;
+
+  /// Card height.
   final double height;
+
+  /// Optional sensor or custom tilt controller.
   final ShinyController? controller;
+
+  /// Color separation strength.
   final double prismatic;
+
+  /// Sparkle strength multiplier.
   final double sparkle;
+
+  /// Main highlight intensity.
   final double specular;
+
+  /// Micro-diffraction intensity.
   final double diffraction;
+
+  /// Global shader opacity multiplier.
+  final double opacity;
+
+  /// Sparkle silhouette specification.
   final SparkleShapeSpec sparkleShape;
+
+  /// Foil style preset.
   final HolographStyle style;
+
+  /// Toggles shader execution.
   final bool enableShader;
 
   @override
@@ -451,6 +566,7 @@ class _ShinyCardState extends State<ShinyCard>
               sparkle: widget.sparkle,
               specular: widget.specular,
               diffraction: widget.diffraction,
+              opacity: widget.opacity,
               sparkleShape: widget.sparkleShape,
               style: widget.style,
               child: base,