Philip Walton is a developer who maintains two very important flexbox resources. The first is the Solved by Flexbox site (philipwalton.github.io/solved-by-flexbox), which offers demos of common layouts implemented using flexbox and all the information you need to create them yourself. Some of the layouts are very difficult to achieve without flexbox.
The second resource is the Flexbugs page at github.com/philipwalton/flexbugs. Flexbox is wonderful, but it is not perfect. Flexbugs provides solutions and workarounds for common problems that developers run into when using flexbox. The information is provided by members of the development community who have encountered these bugs, and the list is well maintained.
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