Design an App Mockup

I am creating a piano app for Chrome. It will be published as an app and as an extension. I need a good CSS designer that will create a build based on flex design, so I'll be able to add buttons and functions later. There are a few CSS pianos online but I wanted something unique. The App itself is online with a temporary design. You can see it here: [login to view URL] and the extension is here: [login to view URL] The piano should feel light and quick, and have some nice animation to make it feel more "real", but the design is mainly up to you. Google store also requires Icons, a screenshot and a promo image. I'll be happy if you could do it also. I'll give further info later. Thanks for reading!