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width: 128,

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height: 128,

50

child: Container(

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+
                          child: AnimatedContainer(

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margin: EdgeInsets.all(margin),

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decoration: BoxDecoration(

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color: color,

You can reference the line numbers in the example code to help track where to
  make these changes in shape-shifting starter code

2. Set starting values for animated properties

{container2 → container3}/lib/main.dart

@@ -40,6 +40,14 @@

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40