I think themes might be closer to what I'm imagining. For example, material versus skeumorphic. But as the OC was talking about interactions, I'd be interested in seeing a scale of assistance or explicitness. For example, at the "I've never used computers before" end of town, there should be lots of inline annotations about what buttons do, lots of dropdown lists, etc. At the "power user" end of the scale there would be keyboard shortcuts, icons, tooltips etc.
