Flax is a game develop tool based on Flash Professional (Later we called it Flash), which is a well-known multimedia creation platform. For the past few years, Flash has even become a powerful game develop tool.
Flax is just to use the power of the Flash to create animation/UI/scene/font etc. Convert a created SWF to texture to be used by other game develop platform, such as PIXI.js and Cocos2d-js.
http://v.qq.com/page/d/a/4/d0148a7pma4.html
If you or your team member especially the artist are familiar with the Flash, you should enjoy it. If you were a Flash game developer, Flax will make you feel so familiar to develop games with other engines like PIXI.JS/Cocos2d etc.
https://github.com/longyangxi/Flax-js-examples
http://longames.com/h5/example/
http://flax.longames.com