FlexBuilder: the best UI framework for Unity3D
For more details, see the Detailed Features page.
Comparison with Unity built-in frameworks
UnityUI
Unity built-in
Unity's built-in UI system
Slow
Works with all AssetStore assets
Works with all existing scripts/code
Live-editing in-game/editor
FlexBuilder
Asset Store
The best of CSS3/Flexbox ... in Unity
Works with all AssetStore assets
Works with all existing scripts/code
Live-editing in-game/editor
Very fast to edit, very fast to refresh
FIXES: core Unity's text-rendering
FIXES: core Unity's slow UI
Implements almost 100% of the CSS3/Flexbox spec
Quick-building UI buttons