1. Add an implicit animation

Change the Container widget to an AnimatedContainer widget:

{container1 → container2}/lib/main.dart

@@ -2,6 +2,8 @@

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// Use of this source code is governed by a BSD-style license

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// that can be found in the LICENSE file.

+
            // ignore_for_file: missing_required_argument

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import 'dart:math';

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import 'package:flutter/material.dart';

@@ -47,7 +49,7 @@

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SizedBox(

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width: 128,