I understand how to theme a standard widget...for instance, CSS for Ext.panel.Panel goes in theme/sass/src/panel/Panel.scss

But how do I theme a widget that I created, e.g. Bespoke.foo.Bar?

I tried creating sass/src/foo/Bar.scss and adding
.foo {
background-color: #F00F00 !important;
Then I ran "sencha package build" on my theme and "sencha app build" on my application, but that line does not appear in any of the generated .css files