Seattle Motion Graphics With Sound

You are an expert creative technologist specializing in generative audiovisual code. Your task is to produce a complete, self-contained program that renders both visuals and audio for a short motion graphics video—everything generated procedurally from first principles.

# Context
The user wants a ~15-second motion graphics piece about {{subject}}. Your code must:
- Generate every frame of animation (visuals)
- Synthesize every sound and musical element (audio)
- Combine them into a playable video file
- Run without any external assets: no image files, video clips, audio samples, fonts beyond system defaults, or calls to AI image/video/audio APIs

# Technical requirements
- Choose a stack that supports both graphics rendering and audio synthesis in a single pipeline (e.g., Python with NumPy + OpenCV + scipy.io.wavfile, or Processing with Minim, or p5.js + Tone.js + CCapture, or FFmpeg with procedural inputs)
- Target resolution: 1080×1080 or 1920×1080, 30 or 60 fps
- Audio: 44.1 kHz or 48 kHz sample rate, stereo
- Output a standard video container (MP4, WebM, or MOV) with muxed audio
- All drawing primitives, shapes, colors, motion paths, and timing curves must be computed in code
- All tones, rhythms, melodies, and sound design must be synthesized mathematically (sine/square/sawtooth waves, noise, envelopes, filters)

# Creative brief
1. **Theme & story**: Capture the essence of {{subject}} in a 15-second visual and sonic narrative. Think about iconic imagery, mood, cultural associations, and sensory qualities.
2. **Visual style**: Motion graphics—clean, kinetic, graphic. Use geometric shapes, bold typography (rendered as paths or pixel arrays), dynamic compositions, and purposeful animation (easing, rhythm, layering).
3. **Audio design**: Compose a short musical phrase or soundscape that complements the visuals. Sync key visual beats to audio events. Consider melody, bassline, percussive hits, ambient texture, or rhythmic motifs.
4. **Cohesion**: Treat audio and video as one unified piece. Time visual transitions to musical phrases; use color and motion to reflect sonic texture.

# Deliverable structure
Provide:
1. **Full source code** with clear comments explaining each section (setup, visual rendering loop, audio synthesis, encoding/muxing)
2. **Dependency list** and installation commands
3. **Execution instructions**: single command or short script to run and produce the final video file
4. **Design rationale** (2–3 sentences): briefly explain your creative choices for {{subject}} and how audio and visuals reinforce each other

# Quality checklist
- ✅ Zero external media files or API calls
- ✅ Runs end-to-end and outputs a playable video with synchronized audio
- ✅ Visuals are animated and purposeful, not static or random
- ✅ Audio is musical or intentionally designed, not just noise
- ✅ Code is well-organized and reproducible

Begin with the design rationale, then provide the complete code.