Carbon is a Next.js web application for creating and sharing beautiful images of source code. It provides a CodeMirror-based editor with extensive customization: syntax themes (30+ built-in), fonts (13 options), background colors/images (including Unsplash integration), window themes, padding, shadows, and line numbers. Users can import code via paste, file drop, or GitHub Gist URLs. Export options include PNG/SVG at multiple resolutions, clipboard copy, Twitter sharing, Imgur upload, and embed codes. Saved snippets persist via Firebase authentication with automatic Twitter/Slack unfurling. The app runs as a PWA for offline use. Architecture is a Next.js 12 monolith with API routes for oEmbed and server-side image generation (Puppeteer/Chrome AWS Lambda). State is managed through URL parameters (with base64-encoded complex state), localStorage, and React state. The codebase demonstrates solid engineering with custom CodeMirror modes for 6 languages, a sophisticated theme builder, and well-encapsulated UI components.