Fake Screencast Agent Skill

fake-screencast — screenshots → simulated screen recording

Make a screenshot walkthrough look like a real screen recording: persistent browser chrome with a URL bar that changes per page, a custom cursor that eases along a bezier path to each click target and ripples on click, page navigation as a hard cut (URL path changes), an in-page filter as a short crossfade (URL query changes), smooth scroll, a slow ken-burns zoom onto the payoff element, and a constant drift so it never looks like a slideshow. TSX-first: controllable, re-renderable, reusable across videos.

This is a beat-building technique inside make-tsx (step 2). Use make-tsx for the timeline.json / render / bake mechanics and the sync-to-words principles; use vidtsx-2d-generator for the low-level rules that keep a Remotion file from crashing (frame-based only, monotonic interpolate, Easing.bezier, no useState/useEffect). The shot you write here follows those rules.

When this is the right tool (decision gate)

• Fake screencast (this skill) — you have or can capture screenshots of the states, and you want a *controlled* walkthrough (cursor path, highlight, zoom, timing synced to narration). This is P4 "real UI for config", just simulated. Best when the walkthrough is about *where things are* / *the steps*, not raw speed.
• Real screen recording — only when the point is genuine proof: real latency, a live result appearing, something you can't fake credibly. Leave a clearly-noted pending_recording placeholder slot until it lands (see make-tsx).
• Single static page clone — if it's one page with no navigation/cursor (e.g. a pricing page you just highlight/scroll), use WebBrowserFrame from lib/browser.tsx directly. Don't reach for the screencast machinery.

Step 1 — get the screenshots (ask the user)

Tell the user the exact shot list you need (one screenshot per page or state the cursor lands on), then wait for them. Requirements:

• Logged in / real data, the actual product UI, captured at a consistent window size (ideally ~1920-wide).
• One per state, including intermediate states: an unfiltered list AND its filtered result count as two screenshots (the crossfade sells the "search applied").
• For a real scroll-through of a long page, you need a tall capture (full page, below the fold) — a single-viewport screenshot can't truly scroll (you can only fake a few px of drift). Say so and ask for the tall one if the beat needs it.
• Ask for any missing view by name (e.g. "the models list filtered to X", "the settings page after toggling Y").

Save them to media/library/images/<service>/ with clear names (account-home.png, workers-ai.png, models-all.png, models-flux.png). Reference in a page as library/images/<service>/<name>.png (that's the staticFile-relative path the component expects).

Step 2 — the library API (remotion/src/lib/screencast.tsx)

<Screencast pages cursor clicks box glow favicon appearAt />. Coordinates are FRACTIONS so they survive any resize:

• cursor x/y and click ripples → VIEWPORT fraction (0..1 of the page area *under* the URL bar).
• zoom fx/fy → IMAGE fraction (transform-origin of the push).

import { Screencast, ScreencastPage, CursorKey } from '../../lib/screencast';

const PAGES: ScreencastPage[] = [
  { img: 'library/images/svc/home.png',  url: 'app.svc.com/…/home',        tabTitle: 'Home | Svc',    enterAt: 0 },
  { img: 'library/images/svc/list.png',  url: 'app.svc.com/…/items',       tabTitle: 'Items | Svc',   enterAt: 130, transition: 'cut' },       // navigation → hard cut + new path
  { img: 'library/images/svc/filtered.png', url: 'app.svc.com/…/items?q=x', tabTitle: 'Items | Svc',  enterAt: 262, transition: 'crossfade', transitionFrames: 5,   // in-page filter → crossfade + same path + query
    drift: 0.01, zoom: { from: 1.0, to: 1.4, fx: 0.32, fy: 0.52, range: [266, 289] } },  // ken-burns onto the payoff card
];

const CURSOR: CursorKey[] = [   // {frame, x, y} in viewport fractions; eased per segment
  { frame: 0, x: 0.60, y: 0.42 }, { frame: 128, x: 0.09, y: 0.68 }, /* … */ { frame: 294, x: 0.36, y: 0.52 },
];
const CLICKS = [130, 206, 255]; // frames a ripple fires (place at the arrival keyframe)

export const compositionConfig = { id: 'SvcRecording', durationInSeconds: 10.0, fps: 30, width: 1920, height: 1080 };
const SvcRecording = () => <Screencast pages={PAGES} cursor={CURSOR} clicks={CLICKS} />;
export default SvcRecording;

Page fields: img, url, tabTitle, enterAt (required); transition?: 'cut'|'crossfade' (default cut), transitionFrames? (default 5), scroll?: {to, range:[a,b], from?} (image px translateY), zoom?: {from,to,fx,fy,range:[a,b]}, drift? (default 0.02 — the constant slow "alive" push). Screencast props: box? (default {x:60,y:63,w:1800,h:954}), glow?, appearAt?, favicon? (default Cloudflare cloud — pass your own for other services).

Step 3 — timing + coordinates

• Frame 0 = the shot's master_in_s. For a narration cue at t seconds: frame = round((t − master_in_s) × fps). Grep edited-transcript.json for the exact word start/end (ms). Put the click / page enterAt a few frames before the word so the *result* lands on the word; end a ken-burns zoom.range on the payoff word.
• Find a click-target fraction from the screenshot: element's pixel position ÷ image width/height ≈ the viewport fraction (the image fills the page region, top-aligned, fit-to-width). Set the cursor's arrival keyframe there and add the click frame ~2f after arrival. Then render and look (Step 4) — nudge the fraction until the pointer sits on the element.
• Sequence each page/cursor move to its cue: dashboard hold on the intro line → cursor eases to a sidebar item and clicks as that item is named → next page appears → zoom to the payoff as the payoff word is spoken.

Gotchas (each of these cost a render to find)

• Zero-height containing block. WebBrowserFrame wraps children in a transformed div, which becomes the containing block for absolute descendants and collapses to 0 height. Page layers therefore need explicit region dims (width/height from the box), not inset:0 — the lib already does this; keep it if you extend it.
• Navigation vs filter is the realism tell. A page change = hard cut + different URL path. An in-page search/filter = short crossfade + same path (query appended). Mixing these up reads as fake.
• Single-viewport screenshots can't scroll — fake "aliveness" with drift + a ken-burns zoom instead. Only use a real scroll when you have a tall capture.
• Render --scale=1 for the preview (1080p, correct for bake.py); re-render --scale=2 for the 4K60 final.
• Cursor hotspot (the tip) is near the pointer SVG's top-left; the lib nudges for it. If a pointer looks a few px off, adjust the target fraction, not the SVG.

Step 4 — verify, then hand back to make-tsx

• Render + screenshot at EACH cue (never one still): node remotion/scripts/render-all.mjs --scale=1 <Id>, then pull frames with ffmpeg at the cursor-on-target frame, each click frame, the page-change frame, and the zoom payoff frame. Confirm the pointer lands on the element, URLs change correctly, and the zoom frames the right thing. Iterate the fractions/frames and re-render.
• Then follow make-tsx for the rest: update timeline.json (swap/retime the span, drop any pending_recording note), python tools/bake.py, and spot-check composited frames of the shot over the real master at the beat + both boundaries.
• If you improve the component (per-page favicons, real typed-text-in-field, a caption layer), promote it back into lib/screencast.tsx so future videos inherit it.

The canonical shape — copy this choreography

The move that reads as a real screen recording, over ~4 captured pages and ~10s:

• Hold on the landing page while the narration sets it up (a beat of drift, never a frozen frame).
• Cursor eases to a sidebar item and clicks on the word that names it — the click lands on the

noun, not before it.

• Hard cut to that page, URL path changes. This is a navigation.
• Type a filter → short crossfade, same path with the query appended. This is not a

navigation, and rendering it as one is the single biggest tell.

• Ken-burns zoom onto the payoff exactly as the payoff word is spoken.

Read remotion/src/lib/screencast.tsx before building one — it's the engine, and its props are

the documentation for every move above. The pages array, the cursor keyframes, the per-page URL and

zoom are all typed there.