> ## Documentation Index > Fetch the complete documentation index at: https://docs.supercycle.com/llms.txt > Use this file to discover all available pages before exploring further. # Developers > Learn about customization, read metafields, and extend the storefront with code For theme developers and agencies. It covers the app blocks you add in the theme editor, the metafields and line item properties Supercycle writes, and the Liquid and JavaScript you can add to a theme. Every app block needs the [Supercycle Engine app embed](/documentation/setup/theme-setup) turned on in the theme. Its **Methods style** settings, the colors, radii, and **Button class**, apply to the app blocks and to the [contract](/documentation/configuration/risk/e-signatures) and [ID verification](/documentation/configuration/risk/identity-verification) pages Supercycle serves through the app proxy. *** ## App blocks Add, position, and customize these blocks from the theme editor. Add every method a product offers to the product page and control the add to cart button. Let customers filter a collection page by rental dates or method. Show your membership plans as cards on any page so customers can join. *** ## Theme code Liquid and JavaScript you paste into a theme to go beyond what the blocks do on their own. Show each method's price on product cards and product pages. Add a switcher between a product sold new and its circular twin. Show plan names, first payments, and recurring totals on cart lines. Style or hide specific method options from CSS or JavaScript. *** ## Reference The data Supercycle writes to Shopify and reads back at checkout. Read the product, variant, and customer metafields Supercycle keeps in sync. Read the schema of the property that turns a cart line into a cycle.