anchor.diff:  // found in the LICENSE file.
   
   import 'dart:io' show Platform;
  -import 'dart:math';
   
   import 'package:flutter/foundation.dart';
   import 'package:flutter/material.dart';
  
positive.code:       );
  
        // Add a tap gesture to collapse the currently opened section.
        if (_state != _DemoState.normal) {
          demoContent = Semantics(
            label: MaterialLocalizations.of(context).modalBarrierDismissLabel,
            child: GestureDetector(
              behavior: HitTestBehavior.opaque,
              onTap: () {
                setStateAndUpdate(() {
                  _state = _DemoState.normal;
                });
              },
              child: ExcludeSemantics(child: demoContent),
            ),
          );
        }
  
        body = SafeArea(
          bottom: false,
  
negative.code:         appBar.preferredSize.height;
      final maxSectionHeight = isDesktop ? contentHeight : contentHeight - 64;
      final horizontalPadding = isDesktop ? mediaQuery.size.width * 0.12 : 0.0;
      final maxSectionWidth = 420.0;
  
      Widget section;
      switch (_state) {
        case _DemoState.options:
          section = _DemoSectionOptions(
            maxHeight: maxSectionHeight,
            maxWidth: maxSectionWidth,
            configurations: widget.demo.configurations,
            configIndex: _configIndex,
            onConfigChanged: (index) {
  