I've seen a couple items in the forum regarding masking and is possibly supported for webkit browsers.
If I wanted to mask an animated object and restrict it from covering another animated object, how do I add the tags in the Sencha CSS area?
Are there any examples of this?
For basic masking (square) you can set the overflow to hidden on the parent object.
For webkit mask, you could add something like this to the custom css property for an object base state. You'll find the 'custom css' property under the 'Other' property group in the property panel.
Here is some Apple/Safari documentation on webkit masking
-webkit-mask-image: -webkit-gradient(linear, left top, left bottom, from(rgba(0,0,0,1)), to(rgba(0,0,0,0)));