FundingCAPTCHA Setup: Rainbow Poop — birds dive-bomb silhouettes #161

A new shader player Setup (ADR-0021) for ShowControl/FundingCAPTCHA/shaders/. This issue is a starting point for fleshing out the design.

Concept

Birds circle overhead and dive-bomb the people they see, splattering them with rainbow poop.

What visitors might see

• Empty room: birds lazily circle or flap across the sky.
• Someone appears: one or more birds pick them as a target, swoop down, and drop a rainbow splat that lands on the silhouette.
• Splats stick: they cling to the person and follow them as they move, maybe dripping or fading over time.
• Dodging: moving fast might make a bird miss, and the poop splats on the ground instead.

Likely building blocks

• Blob records ("blobs") for targeting: a stable slot/ID per person, their centre, and their velocity, so birds can lead a moving target.
• Body .r to clip splats to the silhouette. Splats probably need to be stored in the person's local space (relative to their blob box), not screen space, so they travel with them.
• hunter_bird/ (Hunter bird: a blob-tracker shader Setup, with the blob-records contract #159, Hunter bird: two merged eyes, with lids and blinks inside each eye #160) already has a bird that tracks blobs. It may be reusable as a starting point.

Open questions

• How many birds? Is there one bird per person, or a shared flock?
• How often do they bomb? What cadence keeps it funny without turning into noise?
• Do splats persist for the whole time someone is in frame, or fade?
• What does the rainbow look like: a cartoon blob, paint drips, sparkles?
• What happens when people overlap or swap blob slots?
• What's the duration in rotation?