Demo checkout
You reached the mock checkout.
This site runs the commerce module in mock mode: the catalog and cart are fully functional for demonstration, but no real store is connected, so there is nothing to charge.
In a real project you set PUBLIC_SHOPIFY_STORE andPUBLIC_SHOPIFY_STOREFRONT_TOKEN, and this button hands off to Shopify's own hosted checkout via cart.checkoutUrl. No payment data ever touches the site.