Angular2 Themes


I’m about to start a new project and I’m learning about angular2 and ionic2.

I noticed that ionic2, has a css (sass) core and then some themes for ios, android and windows.

My app will not have many differences between the 3 platforms.

Does ionic have a more neutral theme? Like one for desktop or similar?
Can I force the use of one theme on all the platforms and then customize that theme?