Add custom CSS or JavaScript to Isulium Theme without breaking future updates

Introduction

Add custom CSS or JavaScript to Isulium Theme while preserving upgrade paths for future theme versions.

Where to add custom code

Use document_head.hbs for assets, or extend Isulium Theme-pro.css / script.js with the Developer license. Avoid editing Copenhagen core files when possible.

Safe customization patterns

• Scope CSS with .Isulium Theme- prefixes
• Hook JavaScript on data-Isulium Theme-* attributes
• Keep a changelog of overrides for each Guide upgrade