Frontend Developer for Sports Card Website

I am building a dedicated sports card trading and marketplace website with an established core platform, and we need a talented developer to elevate the user experience (UX), optimize the mobile-first HTML5/CSS3 frontend, and implement critical market functionalities. The ideal candidate must have a strong command of PHP, HTML5, and JavaScript (ES6+) to build out an advanced P2P trading engine with cash-balancing counter-offers, a multi-conditional marketplace filtering system (by sport, player, grading company, and serial number), a live auction engine with real-time bidding, a high-resolution image tool for condition inspection, and an interactive "virtual binder" collection manager, while seamlessly integrating secure payment processing and shipping track-and-trace features into our existing database structure.