I'm seeking an experienced web app developer to create a multi-platform application compatible with desktop, mobile, and tablet devices. Key Requirements: - The app's primary purpose is yet to be defined, but it will fall under one of the following categories: e-commerce, social networking, or information portal. - User authentication through email and password. Ideal Skills and Experience: - Proficiency in responsive web design and development. - Experience in building secure user authentication systems. - Strong background in web apps creation with SQL integration to secure data. - Ability to work within a specified budget and deliver a high-quality product. Please provide a portfolio showcasing similar work.