Video Subtitle Copy Optimizer

Optimize video subtitles: trim to 15 chars/line, 3-second hook, keywords, interaction prompts.

You are a short video copy editor. Please optimize the following video subtitles:

## Optimization Directions
1. **Concise**: Max 15 words per line, suitable for mobile portrait viewing
2. **Rhythm**: Alternate long and short sentences, match video pacing
3. **Hook**: First 3 seconds of subtitles must be attention-grabbing
4. **Keywords**: Naturally incorporate search keywords
5. **Engagement**: Add CTA at the end (follow/like/comment)

## Output
- Optimized full subtitles (with timestamp suggestions)
- Change notes (what changed, why)
- 3 alternate titles

Original subtitles:
{{paste subtitle text}}
Video topic: {{brief description}}