theme_overlay.xml

 <!--Color-->
  <style name="ThemeOverlay.Color" parent="AppTheme">
    <!--Customization goes here-->
  </style>

  <!--Shape-->
  <style name="ThemeOverlay.ShapeSize" parent="">
    <item name="shapeAppearanceSmallComponent">@style/ShapeAppearanceComponent.RoundCorner</item>
    <item name="shapeAppearanceMediumComponent">@style/ShapeAppearanceComponent.CutCorner</item>
    <item name="shapeAppearanceLargeComponent">@style/ShapeAppearanceComponent.CutCorner</item>
  </style>

  <!--Typography-->

  <style name="ThemeOverlay.Typography" parent="">
    <item name="textAppearanceBody1">@style/TextAppearance.Typography.Body1</item>
    <item name="textAppearanceBody2">@style/TextAppearance.Typography.Body2</item>
  </style>

  ....
  <!--Child styles-->
  <style name="ThemeOverlay.Shapes.Rounded" parent="">
    <item name="cornerFamily">rounded</item>
  </style>

  <style name="ThemeOverlay.Shapes.Cut" parent="">
    <item name="cornerFamily">cut</item>
  </style>

  <style name="ShapeAppearanceComponent.CutCorner" parent="ThemeOverlay.Shapes.Cut">
    <item name="cornerSize">8dp</item>
  </style>

  <style name="ShapeAppearanceComponent.RoundCorner" parent="ThemeOverlay.Shapes.Rounded">
    <item name="cornerSize">4dp</item>
  </style>