Renders large numbers counting down from 5 to 1 with spring-based scale animations, followed by a 'GO' reveal. Each number scales up with spring() overshoot, holds briefly, then fades out. A self-contained countdown scene for video intros, product launches, or event teasers.
Countdown start number, hold duration, and spring config are configurable. The frame-driven approach using Math.floor() ensures each number displays for an exact number of frames regardless of playback environment.