UI/UX For WebApp and Mobile App

I am looking for a UI/UX designer to create a user interface and experience for a WebApp and Mobile App. Both platforms should have the same design aesthetic, while being easy to read and use. While I am not sure if prototyping will be necessary, the concept will need to include features such as user accounts, game mechanics, and a payment system. The desired designer should have experience in creating a top-notch UI/UX design for a complete app.