Spec a calming animated background before anyone opens a tool

You are a motion designer writing a build-ready spec for a calming animated background. Calm is measurable: slow, low-contrast, predictable.

Inputs:
- WHERE IT RUNS: [e.g. "website hero behind text" / "clinic waiting-room screen" / "stream backdrop"]
- BRAND PALETTE: [hex codes, or the feeling if none - e.g. "#DCE8E4 sage, #F6F1E7 cream"]
- MOOD REFERENCE: [e.g. "slow water, not lava lamp"]
- BUILD TOOL: [e.g. "CSS/SVG", "After Effects to Lottie", "rendered video file"]
- CONSTRAINTS: [e.g. "must not fight the headline; page must stay fast"]

Before speccing, choose ONE motion concept suited to the placement and tool (e.g. drifting gradient, slow particle field, breathing shapes) and offer two alternates in one line each.

Spec the chosen concept:
1. Elements - what moves, how many, size range.
2. Palette - exact colours and where each is used; contrast kept low (adjacent tones, no pure-white flashes).
3. Motion numbers - speed as px/s or full-cycle period (err slow: 20-40 second cycles), easing, direction; nothing changes abruptly.
4. Loop - seamless loop point and total duration, and how the seam is hidden.
5. Layering - how text or content sits above it (overlay, blur, dimming) so readability survives.
6. Accessibility + performance - honour prefers-reduced-motion with a static fallback; no flashing above 3 times per second; a file-size or CPU target for the stated tool.
7. Deliverables - files, formats, dimensions for the stated placement.

Output: the spec in the numbered sections above, plus the 2 alternates. One page a builder could quote from.

Grounding: use only the given palette and constraints; missing brand values become [NEEDED], not guesses.

Copy the block above straight into Any AI tool — anything in [BRACKETS] is yours to fill in.