Reference
- A Complete Guide to Flexbox (CSS-tricks) – Great overview
- Flexbox playground – Interactive overview of flexbox properties
- Flexbox Playground – another one
Troubleshooting and fallback methods
- flexibility – js polyfill for flexbox. interactive demo
- flexbugs – A community-curated list of flexbox issues and cross-browser workarounds for them.
Practice:
- Flexbox Froggy – A game for learning CSS flexbox
- Flexbox Defense – another game
- Flexbox Game – 28 levels