Paul Scanlon's blog post details the creation of a unique marketing campaign using Gatsby and Shopify, featuring a giveaway of 500 limited edition water bottles. The campaign showcases Gatsby's capabilities as a headless solution by integrating Three.js for a dynamic, synthwave-inspired animation that reflects real-time Shopify inventory levels. This project uses the upgraded gatsby-source-shopify plugin with Shopify's Admin API to effectively handle data sourcing, avoiding the rate limits of the Storefront API. The campaign involves intricate functionalities like dynamic discount code generation and "tinker prevention" to ensure fair distribution of bottles. Additionally, the site utilizes Gatsby Functions to manage checkout processes and includes a feature to map winners' locations using Three.js. Despite challenges with Shopify’s API and marketing requirements, the project exemplifies how Gatsby can extend beyond static site generation to create interactive, JavaScript-rich applications.