Layer voice wave under grid

lib/screens/mapflow_shell.dart

@@ -1359,17 +1359,31 @@ class _VoiceInformationField extends StatelessWidget {
         ),
         LayoutBuilder(
           builder: (context, constraints) {
-            return CustomPaint(
+            final paintSize = Size(
-              size: Size(
               constraints.maxWidth,
               constraints.maxHeight.clamp(300.0, 520.0),
+            );
+            return Stack(
+              alignment: Alignment.center,
+              children: [
+                CustomPaint(
+                  size: paintSize,
+                  painter: _VoiceWaveUnderlayPainter(
+                    samples: samples,
+                    active: active,
+                    liveLevel: liveLevel,
                   ),
+                ),
+                CustomPaint(
+                  size: paintSize,
                   painter: _VoiceInformationPainter(
                     samples: samples,
                     active: active,
                     progress: progress,
                     liveLevel: liveLevel,
                   ),
+                ),
+              ],
             );
           },
         ),
@@ -1378,6 +1392,92 @@ class _VoiceInformationField extends StatelessWidget {
   }
 }
 
+class _VoiceWaveUnderlayPainter extends CustomPainter {
+  const _VoiceWaveUnderlayPainter({
+    required this.samples,
+    required this.active,
+    required this.liveLevel,
+  });
+
+  final List<double> samples;
+  final bool active;
+  final double liveLevel;
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    if (samples.isEmpty) {
+      return;
+    }
+
+    final centerY = size.height * 0.52;
+    final width = math.min(size.width, 420.0);
+    final startX = (size.width - width) / 2;
+    final endX = startX + width;
+    final visibleSamples = samples.length.clamp(24, 96);
+    final sampleStart = math.max(0, samples.length - visibleSamples);
+    final baseline = 12.0 + liveLevel * 34.0;
+    final topPath = Path();
+    final bottomPath = Path();
+
+    for (var index = 0; index < visibleSamples; index++) {
+      final sample = samples[sampleStart + index].clamp(0.0, 1.0);
+      final x = startX + width * (index / math.max(1, visibleSamples - 1));
+      final phase = index * 0.52;
+      final lift = baseline + sample * 112.0;
+      final softWave = math.sin(phase) * (8.0 + liveLevel * 14.0);
+      final y = centerY - lift * 0.5 + softWave;
+      final mirrorY = centerY + lift * 0.5 - softWave;
+      if (index == 0) {
+        topPath.moveTo(x, y);
+        bottomPath.moveTo(x, mirrorY);
+      } else {
+        topPath.lineTo(x, y);
+        bottomPath.lineTo(x, mirrorY);
+      }
+    }
+
+    final fillPath = Path.from(topPath)
+      ..lineTo(endX, centerY)
+      ..lineTo(endX, centerY)
+      ..addPath(bottomPath, Offset.zero)
+      ..lineTo(startX, centerY)
+      ..close();
+    final alpha = active ? 0.10 + liveLevel * 0.16 : 0.05;
+    final fillPaint = Paint()
+      ..shader = LinearGradient(
+        begin: Alignment.centerLeft,
+        end: Alignment.centerRight,
+        colors: [
+          const Color(0xFF38F5D3).withValues(alpha: alpha * 0.35),
+          const Color(0xFFFF2D75).withValues(alpha: alpha),
+          const Color(0xFFFF7A90).withValues(alpha: alpha * 0.65),
+        ],
+      ).createShader(Rect.fromLTWH(startX, 0, width, size.height))
+      ..style = PaintingStyle.fill
+      ..maskFilter = const MaskFilter.blur(BlurStyle.normal, 18);
+    canvas.drawPath(fillPath, fillPaint);
+
+    final strokePaint = Paint()
+      ..color = const Color(
+        0xFFFF6B8A,
+      ).withValues(alpha: active ? 0.22 + liveLevel * 0.28 : 0.08)
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = 2.4 + liveLevel * 3.0
+      ..strokeCap = StrokeCap.round
+      ..strokeJoin = StrokeJoin.round
+      ..maskFilter = const MaskFilter.blur(BlurStyle.normal, 5);
+    canvas.drawPath(topPath, strokePaint);
+    canvas.drawPath(bottomPath, strokePaint);
+  }
+
+  @override
+  bool shouldRepaint(covariant _VoiceWaveUnderlayPainter oldDelegate) {
+    return oldDelegate.samples != samples ||
+        oldDelegate.active != active ||
+        oldDelegate.liveLevel != liveLevel;
+  }
+}
+
 class _VoiceInformationPainter extends CustomPainter {
   const _VoiceInformationPainter({
     required this.samples,