The Senior Software Engineer focuses on the user-interface, or client-presentation layer. They specialize and are expert at advanced cross-browser & cross-platform HTML, HTML semantics, CSS, DOM, JavaScript, HTTP/URL; with strong knowledge of progressive enhancement / graceful degradation, browser developer tools, responsive & adaptive web design & development, mobile & web performance; knowledge of SEO, interaction and/or user-interface design; user experience & usability; and strong knowledge of Photoshop, Zeplin, Figma, and similar tools.