The context
A semi-fine jewellery brand selling through Instagram, with no place of its own to send people who ask for a price. The site had to sustain the perception of a premium product and end the conversation on WhatsApp, which is where the sale actually happens.
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No cart, on purpose
A full checkout would be the wrong call here: the volume does not pay for running payments and shipping, and selling jewellery like this goes through a conversation — matching pieces, lead time, hand delivery. The button opens WhatsApp with the piece already named in the message.
Built in HTML, CSS and JavaScript, with no framework. It is a page that rarely changes and has to load fast on 4G — build complexity would not pay for itself.