The cart as a sheet from the right (a bottom sheet on a phone): lines with a quantity and Remove undone from a toast, and a summary with a free-shipping meter, a rolling subtotal and Check out. Plus the header's cart button, Add to cart with its Added state, and useCartState, a cart in memory.
pnpm dlx shadcn@latest add "https://littmd.vercel.app/r/cart.json"