Build an interactive ferrofluid simulation. A pool of magnetic liquid must react to one or more magnets the user can drag around, forming spikes and ridges that follow the magnets and relax when they move away. It must also do something interesting on its own when nobody is touching it. How it looks and feels is your decision. Show a small hint that the magnets can be dragged.

Everything about the design is your decision: style, colors, mood, environment, camera, level of detail, and any extra touches. Do not ask me any questions, make every choice yourself and build the most impressive version you can in a single attempt.

Technical requirements: one single self-contained HTML file, no external models, images, sounds, or asset URLs of any kind (a JavaScript library from a CDN is fine). It must start running on its own the moment it loads, with no clicks needed, and run smoothly with no console errors.