Using slivers to achieve fancy scrolling
A sliver is a portion of a scrollable area that you can define to behave in a special way. You can use slivers to achieve custom scrolling effects, such as elastic scrolling.
For a free, instructor-led video workshop that also uses DartPad, check out the following video about using slivers:
Resources
For more information on implementing fancy scrolling effects in Flutter, see the following resources:
- Slivers, Demystified
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    A free article on Medium that explains how to implement custom scrolling using the sliver classes. 
- SliverAppBar
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    A one-minute Widget-of-the-week video that gives an overview of the SliverAppBarwidget.
- SliverList and SliverGrid
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    A one-minute Widget-of-the-week video that gives an overview of the SliverListandSliverGridwidgets.
- Slivers explained - Making dynamic layouts
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    A 50-minute episode of The Boring Show where Ian Hickson, Flutter’s Tech Lead, and Filip Hracek discuss the power of slivers. 
API docs
Here some links to relevant API docs: