I need a ready-to-install Shopify app or custom plugin that lets my customers see real-time shipping costs while they browse. The two core functions I must have are rate comparison across my predefined shipping options and clear delivery-time estimates next to every rate. Costs should be calculated strictly on a weight-based formula that I will supply. Because I am still evaluating carriers, the code should be flexible enough to accept additional APIs later; at launch it can pull data from any single carrier you already support. A clean settings panel inside the Shopify admin is important so that my team can adjust weight brackets and handling fees without touching code. Before we get started, please provide a live demo or staging-store link that shows the calculator in action inside the cart or checkout so I can verify speed and UX. Deliverables • Packaged Shopify app or installable custom plugin • Quick-start documentation covering setup, weight table editing, and carrier/API switching • Short loom or screen-share walkthrough of the live demo/store I’m ready to move quickly once I see a working example that matches the requirements.