Let's design a system for creating and managing short-form video content, similar to TikTok or Instagram Reels. The core challenge lies in enabling users to easily create engaging content by layering various effects, transitions, and audio tracks on top of video clips. This isn't just about stitching videos together; it's about providing a rich editing experience that empowers creativity while abstracting away the underlying complexities.

Imagine a user wants to create a 15-second video. They might:

1. Record several short video clips (e.g., 3 clips of 5 seconds each).
2. Add a filter to one or more clips (e.g., a vintage filter).
3. Apply a transition between the first and second clips (e.g., a fade transition).
4. Overlay text and stickers at different points in the video. These elements should be animated (e.g., the text flies in from the left).
5. Add background music.
6. Adjust the volume of the original audio in the clips.

The system must be designed to handle these operations efficiently and allow for future expansion with new types of effects, transitions, and interactive elements. We need to ensure the design promotes code reusability, testability, and maintainability.

The core of the system is the Composition. This object represents the final, assembled video. It is comprised of Track objects. Each Track can contain Clip objects, Effect objects, Transition objects, and Overlay objects. The system must orchestrate the application of these elements at the correct timestamps to create the final output video. The rendering pipeline is a key consideration.

Requirements