content: // Flutter imports:
  import 'package:flutter/material.dart';
  
  RouteTransitionsBuilder parallaxSlideInTransitionBuilder(
    Widget enterWidget,
    Widget oldWidget,
  ) =>
      (context, animation, secondaryAnimation, child) => Stack(
        children: [
          SlideTransition(
            position:
                Tween<Offset>(
                  begin: Offset.zero,
                  end: const Offset(-1, 0),
                ).animate(
                  CurvedAnimation(
                    parent: animation,
                    curve: Curves.fastOutSlowIn,
                  ),
                ),
            child: oldWidget,
          ),
          SlideTransition(
            position:
                Tween<Offset>(
                  begin: const Offset(1, 0),
                  end: Offset.zero,
                ).animate(
                  CurvedAnimation(parent: animation, curve: Curves.fastOutSlowIn),
                ),
            child: enterWidget,
          ),
        ],
      );
  
  RouteTransitionsBuilder leftToRightTransitionBuilder() =>
      (context, animation, secondaryAnimation, child) => SlideTransition(
        position:
            Tween<Offset>(
              begin: const Offset(1, 0),
              end: Offset.zero,
            ).animate(
              CurvedAnimation(
                parent: animation,
                curve: Curves.fastOutSlowIn,
              ),
            ),
        child: child,
      );
  
  RouteTransitionsBuilder fadeTransitionBuilder() =>
      (context, animation, secondaryAnimation, child) => FadeTransition(
        opacity:
            Tween<double>(
              begin: 0, // Start with a fully transparent page
              end: 1, // End with a fully opaque page
            ).animate(
              CurvedAnimation(
                parent: animation,
                curve: Curves.easeInSine,
                reverseCurve: Curves.easeOutSine,
              ),
            ),
        child: child,
      );
  