Overlays

Overlays let you place additional media on top of the recording timeline. Use them for intros, transitions, corner branding, callouts, or short contextual clips that would be awkward to build inside the browser automation itself.

An overlay’s content comes from exactly one source: a file path, an inline React element, inline jsx/solidJsx component source, or an inline html fragment.

For a file path, the extension selects what it is:

• .tsx — a React component module rendered client-side in the browser (hooks, effects, class lifecycle all run). See Component page overlays.
• .solid.tsx — a Solid component module, same treatment with Solid’s compiler.
• .vue — a Vue single-file component (its <style> block included).
• .svelte — a Svelte component (its <style> block included).
• .html — a full standalone HTML document, loaded as-is (its own <style>/<script> run).
• .svg / .png — an image.
• .mp4 — a video.

The inline variants keep small overlays in the recording file itself (see Inline overlays):

• element — a React element (element: <Badge label="New" />), rendered in-process to static markup.
• jsx / solidJsx — the source of a component module as a string, bundled and mounted client-side like a .tsx/.solid.tsx file.
• html — an HTML fragment placed in the overlay root.

Every rendered variant (everything except image/video files) is rendered to a transparent PNG at recording time and then behaves exactly like an image overlay, or, with animate: true, is captured as a transparent animated clip (see Animated overlays).

Overlays can be owned by code or handed to Editor (the web app where non-developers swap the assets); see the two ways to declare overlays below.

You will learn

• how to declare overlays (code values or Editor-owned)
• how to define overlays
• how to position and size overlays
• how blocking and start/end timing work
• how to organize files for maintainable projects

Two ways to declare overlays

There are two ways to declare overlays, and both are editable in the web app. The same two forms apply to narration, values, and audio. See the Editor guide for how the web editing works.

1. Code values. You point each overlay at a file, element, or config. The code values are used until the overlay is edited in Editor, and from then on the Editor value wins.

video.overlays({ logo: { path: 'assets/logo.png', x: 96, y: 96, width: 288 } })

2. Editor-owned (blank). Pass a bare array of overlay names: the names exist in code (so the body can call overlays.logo), but Editor owns the files and display options.

import { video } from 'screenci'

video.overlays(['intro', 'logo'])

Define overlays

video.overlays(...) takes a map. Each value is one of:

• a file path string (.tsx, .solid.tsx, .vue, .svelte, .html, .svg, .png, .mp4),
• a React element (badge: <Badge label="New" />, shorthand for { element: ... }),
• a config object ({ path, ...placement }, or one of the inline sources element/jsx/solidJsx/html),
• a factory (props) => config (see Programmatic overlays), or

A config draws its content from exactly one source. Component overlays (.tsx/.solid.tsx/.vue/.svelte files, jsx/solidJsx source) accept serializable props; only .mp4/image files accept the video/crop fields.

import { video } from 'screenci'

video.overlays({
  intro: { path: 'assets/intro.mp4', fill: 'screen' }, // full-frame video
  hint: 'assets/callout.html', // full HTML page
  badge: {
    path: 'overlays/Badge.tsx',
    props: { label: 'New' },
    x: 1340,
    y: 110,
  }, // React component page
  note: { html: '<div class="note">Tip</div>', x: 1340, y: 320, width: 380 }, // inline fragment
  stamp: <Stamp label="Beta" />, // inline React element
  logo: { path: 'assets/logo.png', x: 96, y: 96, width: 288 }, // image
})('Overview', async ({ page, overlays }) => {
  await overlays.intro()
  await page.goto('/dashboard')
  await overlays.logo.for(1200)
})

video.overlays({...}) returns a builder you call with the usual (title, body) arguments. Each key becomes a callable overlay controller, delivered to the body through the injected overlays fixture. The same pattern works for screenshots: screenshot.overlays({...})('Title', async ({ page, crop, overlays }) => {...}).

You can also declare overlay names alone with a bare array and upload the files plus display options on the Editor page instead of keeping them in the repository: video.overlays(['intro', 'logo']). This form leaves the file and placement for each name configured in the ScreenCI web app. Overlays declared with code values stay editable too: the code values are used until the overlay is edited in Editor, and from then on the Editor value wins. See Editor.

For per-language overlay files (e.g. a translated badge image), see Languages.

Overlay files (.png, .mp4, .svg) are uploaded the first time you record with them present and reused on later runs, so you do not have to commit the files. If a file is missing locally, ScreenCI reuses the version uploaded for this video (matched by the overlay’s name). See Asset files do not need to be committed.

Rules:

• every overlay except .mp4 needs a length: give it a relative .for(1200) / .for(1200), an absolute .until('0:05')/.until('56%'), a duration config string or millisecond number, or drive it with start()/end(). A bare overlays.logo() is invalid for these (it only works for a video or render dependency, which holds for its natural length).
• rendered page and image overlays do not support volume.
• .mp4 overlays may provide volume (a linear gain). 1 (the default) plays the source at its natural level, 0 mutes it, and values above 1 boost it (e.g. 2 is twice as loud, up to 4).
• .mp4 overlays use the file’s natural duration and must not provide a duration.
• .mp4 overlays may provide speed or time to play the clip (and its audio) faster or slower. speed is a multiplier (2 plays it twice as fast, 0.5 at half speed); time is a target playback duration in ms (the clip is sped up or slowed down to play over exactly that long). Set at most one. This sets how long the (sped) clip plays for, since both a blocking call (await overlays.intro()) and a live start()/end() window play the clip out to its end; later content shifts to make room. Use it (or trimming) to make a clip run shorter. Rendered page and image overlays do not support speed/time.

Cropping a file overlay

Image (.svg/.png) and video (.mp4) overlays accept a crop rectangle that selects a region of the source file, in the source’s own pixels (top-left origin), just like Playwright’s page.screenshot({ clip }). The cropped region is then placed and scaled like any other overlay. crop is not supported for rendered page overlays.

const overlays = createOverlays({
  // Show only the left panel of a wide screen recording.
  panel: { path: 'demo.mp4', crop: { x: 0, y: 0, width: 960, height: 1080 } },
  // Crop a badge out of a sprite sheet and place it top-right.
  badge: {
    path: 'sprites.png',
    crop: { x: 128, y: 0, width: 96, height: 96 },
    x: 1740,
    y: 64,
    width: 96,
  },
})

x, y must be >= 0 and width, height > 0.

Trimming a video overlay (start / end)

.mp4 overlays accept start and end time strings to play only a slice of the source: a late start and/or an early end. Both are absolute positions in the source clip, expressed as a time string: '2s'/'1.5s', a '0:02'/'0:02.5' timecode, or '50%' of the source duration. start must come before end. Trimming shortens how long the overlay occupies the timeline (before any speed/time).

const overlays = createOverlays({
  // Play seconds 2 through the halfway point of the source clip.
  clip: { path: 'demo.mp4', start: '0:02', end: '50%' },
})

start/end apply to .mp4 overlays only (images have no timeline).

Component and .html page overlays

A custom overlay is a full page you author, in one of two forms:

• A component page (path ends in .tsx, .solid.tsx, .vue, or .svelte): a module that default-exports a component, rendered client-side in the browser during capture. The full framework runtime runs, so hooks/effects/signals, lifecycle and state, styles, and class bindings all work, and Vue/Svelte <style> blocks are carried into the overlay. Component overlays accept serializable props (declare them with defineProps in Vue, $props() in Svelte). screenci bundles them with vite (an optional peer dependency, resolved from your project together with the framework itself: react/react-dom for .tsx, solid-js + vite-plugin-solid for .solid.tsx, vue + @vitejs/plugin-vue for .vue, and svelte (v5+) + @sveltejs/vite-plugin-svelte for .svelte).
• A .html page (path ends in .html): a complete standalone HTML document, loaded as-is. Its own <style> and <script> run (the script is advanced by the virtual clock when animate: true).

Both render to a transparent PNG (or, with animate: true, an animated clip), then place exactly like an image overlay.

video.overlays({
  // A React page, parameterized by props.
  badge: {
    path: './overlays/Badge.tsx',
    props: { label: 'New' },
    x: 1340,
    y: 96,
    width: 240,
  },
  // A full HTML page.
  hint: { path: './overlays/callout.html', x: 768, y: 864, width: 384 },
})('Overview', async ({ overlays }) => {
  await overlays.badge.for(1500)
  await overlays.hint.for(1200)
})

Transparent background. A page overlay owns its whole document, so make its background transparent (otherwise it paints an opaque rectangle over the recording):

callout.html

<!doctype html>
<html>
  <head>
    <style>
      html,
      body {
        margin: 0;
        background: transparent;
      }
      .callout {
        /* ... */
      }
    </style>
  </head>
  <body>
    <div class="callout">Saved</div>
  </body>
</html>

A .tsx page’s generated host document is already transparent; just avoid an opaque root element.

Sizing. The overlay is captured content-sized: screenci screenshots the element with id="screenci-overlay-root" if the page has one, else the document <body>. A .tsx page mounts into that root for you. For a .html page, wrap your content in <div id="screenci-overlay-root">…</div> for tight sizing (or let it fall back to the body box). The width/height placement then scales that captured image onto the frame, so the output size never has to be known when you author.

A .tsx page is a full React component. Author it exactly as you would an app component: import React, hooks, helpers, child components. Only serializable props cross into it (they are JSON-encoded), so pass plain data, not functions or elements.

// overlays/Counter.tsx — hooks and effects run during capture
import { useEffect, useState } from 'react'

export default function Counter({ to }: { to: number }) {
  const [n, setN] = useState(0)
  useEffect(() => {
    const start = Date.now()
    let raf = 0
    const tick = () => {
      const t = Math.min(1, (Date.now() - start) / 2000)
      setN(Math.round(t * to))
      if (t < 1) raf = requestAnimationFrame(tick)
    }
    tick()
    return () => cancelAnimationFrame(raf)
  }, [to])
  return <div className="counter">{n}</div>
}

// the recording
video.overlays({
  counter: {
    path: './overlays/Counter.tsx',
    props: { to: 100 },
    animate: true,
    duration: 2000,
  },
})('Overview', async ({ overlays }) => {
  await overlays.counter() // counts 0 -> 100 over 2s
})

Class components work identically (this.props, this.state, componentDidMount, etc.). A .tsx page needs react, react-dom, and vite installed in your project.

The same pattern works in the other frameworks; only the module changes:

overlays/Badge.vue

<script setup>
defineProps({ label: { type: String, default: 'New' } })
</script>
<template>
  <div class="badge">{{ label }}</div>
</template>
<style>
.badge {
  /* carried into the overlay automatically */
}
</style>

A .solid.tsx module default-exports a Solid component (the compound extension keeps Solid’s JSX compiler away from React .tsx files), and a .svelte module is a regular Svelte 5 component using $props().

Inline overlays

Small overlays do not need their own file. Three inline sources keep the content in the recording file itself:

element takes a React element and renders it in-process to static markup. Because it renders in your recording process, props are baked into the JSX and you can close over any test-scope value directly; there is no separate props field. No client JS runs (hooks and effects do not fire), but CSS animations still play under the virtual clock with animate: true. A bare element is shorthand for the config form:

const label = await page.textContent('#plan') // close over runtime values

video.overlays({
  badge: <Badge label="New" />, // shorthand
  plan: { element: <PlanCard name={label} />, x: 1340, y: 110, width: 288 },
})

jsx (React) and solidJsx (Solid) take the source of a component module as a string, bundled and mounted client-side exactly like a .tsx/.solid.tsx file, so the full runtime runs (hooks, effects, requestAnimationFrame). The source is compiled in isolation for the browser: it cannot close over test variables; pass data through the serializable props instead. Imports inside the string resolve relative to the recording file’s directory.

video.overlays({
  counter: {
    jsx: `
      import { useEffect, useState } from 'react'
      export default function Counter({ to }) {
        const [n, setN] = useState(0)
        useEffect(() => { /* animate n towards to */ }, [to])
        return <div className="counter">{n}</div>
      }
    `,
    props: { to: 100 },
    animate: true,
    duration: 2000,
  },
})

html takes an HTML fragment and places it in the overlay root. Include a <style> tag in the fragment for styling; scripts are not executed (use a .html file overlay for a page that owns its own scripts).

video.overlays({
  note: {
    html: '<div class="note"><style>.note{padding:8px}</style>Tip</div>',
    x: 1340,
    y: 110,
    width: 380,
  },
})

Which variant runs client JS:

Variant	Client JS (hooks/effects)	Closes over test scope	props
.tsx / .solid.tsx / .vue / .svelte files	yes	no	yes
jsx / solidJsx source	yes	no	yes
element	no (static render)	yes	no
html fragment	no (styles only)	yes (via template)	no
.html file	yes (its own scripts)	no	no

Programmatic overlays (props)

Instead of a static value, an overlay can be a factory (props) => config. The factory runs each time you call the overlay, so its path, props, and placement can depend on values you only know at runtime. Call overlays.name(...) to get a controller, then drive it the usual way (.for(...), .until(...), start(), end()):

video.overlays({
  // Props select the .tsx page's content and its placement.
  badge: (p: { label: string; x: number }) => ({
    path: './overlays/Badge.tsx',
    props: { label: p.label },
    x: p.x,
    y: 110,
    width: 288,
  }),
})('Overview', async ({ page, overlays }) => {
  await overlays.badge({ label: 'Saved', x: 1340 }).for(1200)

  // For start()/end(), capture the controller so the props appear once.
  const badge = overlays.badge({ label: 'New', x: 1340 })
  await badge.start()
  await page.click('#next')
  await badge.end()
})

To position an overlay over a live element, combine a factory with an over locator (see Positioning over a live element): screenci reads the element’s box at recording time and sizes the overlay to it.

Page overlays are rasterized after the test body finishes, not inline while it runs. The resolved page (and, for a component overlay, its bundle and props) is captured during the test; overlays with identical content are then rasterized just once (and unchanged overlays are served from a cross-run cache). You do not need to record the same overlay repeatedly.

Animated overlays

By default a page overlay is captured as a single still frame. Set animate: true to play its animation back in the video, with the transparent background preserved.

video.overlays({
  // A .tsx page whose effect/CSS animates in.
  intro: {
    path: './overlays/Intro.tsx',
    animate: true,
    duration: 1500,
    fill: 'screen',
  },
  // An animated .html page, captured at 60fps.
  hint: {
    path: './overlays/callout.html',
    animate: true,
    duration: 1200,
    fps: 60,
  },
})('Overview', async ({ overlays }) => {
  await overlays.intro() // plays the 1.5s animation over a frozen frame
})

How the animation is driven and how long it runs:

• Deterministic clock. Capture advances a virtual clock one frame at a time, so everything time-based is reproducible: CSS animations/transitions, and a page’s setTimeout/setInterval, requestAnimationFrame, Date.now()/ performance.now(), and the Web Animations API (including React effects in a .tsx page). Schedule an edit at t ms and it lands on the matching frame, every run.
• Length. You set the length explicitly: use .for(2000) on the call or set duration in the config. When you drive an animated overlay with start()/end(), duration is required in the config (the capture length is otherwise unknown). If the live window outlasts the clip, its last frame is held; if the clip outlasts the window, end() plays the remaining animation out over a frozen frame before the timeline continues.
• fps sets the capture frame rate (defaults to 30) and only applies with animate: true.
• Reserve room for growth. The overlay is captured at its initial layout box. If the animation grows the content (adds lines, expands a panel) or moves beyond its box (a transform that translates/scales out), size the page’s root to its final dimensions up front (or add your own padding), so nothing is clipped. Animating transform/opacity within the box is free.

Capturing many frames is heavier than a single screenshot, so prefer short durations for full-screen animations.

Positioning

Placement fields are flat on the config and each defaults independently. Coordinates are CSS pixels of the recording viewport, the same space Playwright’s boundingBox(), page.mouse, and viewportSize() use, with the overlay anchored at its top-left corner. The renderer maps these recording-viewport pixels into the final output frame, so the output size never has to be known when you author: the same placement renders correctly at 720p, 1080p, 4K, or vertical.

video.overlays({
  // Top-left badge, 288 px wide (on a 1920x1080 recording).
  badge: {
    path: 'assets/badge.png',
    duration: 1500,
    x: 96,
    y: 96,
    width: 288,
  },
  // A banner across the full output frame, sized by height.
  label: {
    path: 'assets/label.svg',
    duration: 1500,
    relativeTo: 'screen',
    x: 192,
    y: 864,
    height: 108,
  },
})('Overview', async ({ page, overlays }) => {
  // ...
})

• relativeTo: 'recording' (the default) positions against the composited recording area (which may be inset when renderOptions.recording.size < 1). Pixels are measured in the recording viewport, so the box stays correct whatever output size you settle on later in the studio.
• relativeTo: 'screen' positions against the full output frame, using the same recording-pixel scale measured from the output’s top-left.
• x and y are the top-left corner in CSS px. Both default to 0.
• Provide one of width or height (in CSS px). The other is derived from the overlay’s intrinsic aspect ratio (or from aspectRatio, given as width / height) so it is never distorted.

When no placement field is set, the overlay fills the recording area (the renderer resolves this, since it knows the recording size). To fill explicitly, set fill: 'recording' fills the recording area (the same as omitting placement), and 'screen' fills the entire output frame.

Overlays and zoom (pinToScreen)

By default an overlay is “burned” into the scene: when the camera zooms or pans (a zoomTo or an auto-zoom), the overlay moves and scales with the recording underneath it. So a ring placed over an element stays glued to that element as you zoom into it, and a badge anchored to part of the recording tracks that part.

Set pinToScreen: true to keep an overlay stuck to the screen instead: it holds a fixed position and size in the output frame, unaffected by zoom. Use it for HUD-style elements that should stay put, such as a persistent corner logo or a watermark-like badge:

video.overlays({
  // Stays in the corner at a fixed size, even while the recording zooms.
  cornerLogo: (p: { x: number; y: number }) => ({
    path: 'assets/logo.png',
    relativeTo: 'screen',
    x: p.x,
    y: p.y,
    width: 120,
    pinToScreen: true,
  }),
})('Overview', async ({ page, overlays }) => {
  // ...
})

pinToScreen is orthogonal to placement: it works with relativeTo: 'recording' / 'screen', a fill overlay, or an over element. It only affects how the overlay behaves under zoom (whether it is burned into the scene or fixed to the screen).

Drawing above the cursor (overMouse)

Set overMouse: true to draw an overlay above the mouse cursor, so the cursor passes underneath it instead of on top. The cursor stays visible everywhere else in the frame; only where the overlay sits does the overlay cover it. This is handy for full-screen intro or outro cards (the cursor disappears behind the card) and for HUD elements like a corner logo the cursor should slide under:

video.overlays({
  logo: {
    path: 'assets/logo.png',
    fill: 'screen',
    duration: 2000,
    overMouse: true,
  },
})('Product demo', async ({ page, overlays }) => {
  // The cursor slides under the 2s card, then sits on top again for the walkthrough.
  await overlays.logo.for(2000)
  // ...
})

overMouse works for both blocking overlays (.for() / .until()) and live overlays driven with start() / end(). It is placement-agnostic, so it applies to every overlay variant. A few details:

• The overlay keeps its placement: a pinToScreen overlay stays fixed in screen space, a burned overlay still moves and scales with the camera during zoom. overMouse only changes its stacking order relative to the cursor.
• Overlapping overMouse overlays each draw above the cursor.
• It has no effect on screenshots, whose cursor is hidden by default (see renderOptions.screenshot.mouse.show).

Positioning over a live element

To frame or circle a real element, give a programmatic overlay an over locator (and an optional margin in CSS px). screenci reads the element’s box at recording time, sizes the overlay to it (plus the margin), and positions it over the element. Your overlay content fills that box, so a ring lands exactly around the element:

import type { Locator } from '@playwright/test'
import { video } from 'screenci'

video.overlays({
  // A .html page whose content fills the element's box (width/height: 100%).
  ring: (target: Locator) => ({
    path: './overlays/ring.html',
    over: target,
    margin: 8, // optional breathing room around the element
  }),
})('Overview', async ({ page, overlays }) => {
  const save = page.getByRole('button', { name: 'Save' })
  const ring = overlays.ring(save) // capture the controller, then drive it
  await ring.start()
  await save.click()
  await ring.end()
})

overlays/ring.html

<!doctype html>
<html>
  <head>
    <style>
      html,
      body {
        margin: 0;
        background: transparent;
      }
      .ring {
        width: 100%;
        height: 100%;
        box-sizing: border-box;
        border: 4px solid #ec4899;
        border-radius: 12px;
      }
    </style>
  </head>
  <body>
    <div class="ring"></div>
  </body>
</html>

over works with every rendered page overlay (component files, .html, element, jsx/solidJsx, and inline html). It is always recording-relative and overrides x/y/width/height/relativeTo/fill. Make the content fill its box (width:100%;height:100%). Repeated calls with the same element box rasterize only once.

Add animate: true and the ring plays its CSS animation back in the video while the page keeps being driven underneath. Here is that same margin ring, pulsing around a live element (the Screenshots guide shows the still version):

Show source

import type { Locator } from '@playwright/test'
import { video } from 'screenci'

// Animates the same ring as the Screenshots still: it pulses while the page is
// driven underneath, then closes before the recording stops. An opacity-only
// pulse keeps the ring landed exactly on the element (no scale, so no capture
// padding is needed).
video.overlays({
  // A full .html page whose CSS pulses the ring; `over` sizes it to the element.
  ring: (target: Locator) => ({
    path: './assets/ring-animated.html',
    over: target,
    margin: 6,
    animate: true,
    duration: 2400,
  }),
})('Locator highlight (animated)', async ({ page, overlays }) => {
  await page.goto('https://screenci.com/')

  const cta = page.getByRole('link', { name: 'View Documentation' })
  await cta.scrollIntoViewIfNeeded()

  // The ring pulses while the page stays live. Every start() must be ended
  // before the video function returns.
  const ring = overlays.ring(cta)
  await ring.start()
  await cta.hover()
  await ring.end()
})

overlayRect (lower-level)

If you need the element’s coordinates yourself (for example to pass into a component that draws relative to the element), call overlayRect(locator, opts?). It returns the box in CSS px of the recording viewport:

const rect = await overlayRect(page.getByRole('button', { name: 'Save' }), {
  margin: 8,
})
// rect.x / rect.y / rect.width are CSS px; rect.pixels -> the full CSS-px box.
// Top-level relativeTo/x/y/width spread into a placement: { ...rect }

Options: margin (px around the element), dimension ('width' by default, or 'height' to expose that axis at the top level), and relativeTo ('recording' by default; 'screen' is only meaningful when the recording fills the output frame). Make sure the element is visible first; it throws if the locator has no box.

Timing and control flow

Every controller supports two timing styles.

Blocking holds the overlay over a frozen frame for a fixed duration, then the script continues:

await overlays.badge() // uses the config duration
await overlays.badge.for(2000) // or override the duration

Until a position keeps the overlay on a frozen frame until an absolute point in the finished video, instead of a relative duration. Pass a string position:

await overlays.tip.until('0:10') // visible until 10 seconds in
await overlays.tip.until('2s') // seconds (fractions allowed: '5.51s')
await overlays.tip.until('1:02:03.5') // h:mm:ss(.f) timecode
await overlays.tip.until('56%') // until 56% through the video

Positions are resolved against the finished render, so they line up with the actual video. Supported for image, HTML, and React (static) overlays, and for embedded-render overlays. They are not supported for .mp4 or animated overlays, whose length is fixed (use start()/end() for those). A position at or before where the overlay appears is ignored with a warning.

start() / end() keeps the overlay on screen while the page keeps being driven underneath, so it stays live over your real interactions:

await overlays.badge.start()
await page.click('#next')
await page.fill('#email', '[email protected]')
await overlays.badge.end()

For an overlay with an intrinsic length (a .mp4 video, an embedded video dependency, or an animated HTML/React clip), end() lets the clip finish: if the media is longer than the live window, the remainder plays out over a frozen frame before the timeline continues, so the clip is never cut short by ending early. To show less of such a clip, trim it (start/end or speed/time) instead of calling end() sooner. Length-less overlays (images and non-animated rendered pages) end exactly at end().

Overlays can overlap. Several can be live at the same time, and a blocking overlay can run while others stay live, so you can layer them freely:

await overlays.badge.start()
await overlays.logo.start() // both live now
await page.click('#next')
await overlays.tip.for(1500) // blocking overlay, badge and logo stay composited
await overlays.badge.end() // end each one independently, in any order
await overlays.logo.end()

Every overlay you start() must be end()ed before the video function returns, and the same overlay cannot be started twice without ending it in between. Leaving an overlay open, or restarting one that is already live, raises an error.

Narration runs independently of overlays, so you can narrate while an overlay is on screen.

Other timing notes:

• video overlays (.mp4) use the media file’s natural duration and play at their natural level (volume defaults to 1); set volume to mute (0) or boost (above 1, up to 4)
• full-screen overlays take over the output frame
• overlays stay on top of the recording while the underlying screen continues

That means you do not need separate timing math just to line an intro clip up with the next step.

File organization

A simple structure is usually enough:

assets/
  intro.mp4
  transition.mp4
  callout.html
  badge.svg
  logo.png

Keep reusable brand assets separate from throwaway experiment files so the project stays readable.

Authoring advice

• Use overlays sparingly.
• Mute overlays that should not compete with narration.
• Keep intros and transitions short.
• Prefer short .for(...) (or duration) values for image overlays so they do not stall the timeline longer than needed.
• Prefer consistent placement and sizing across videos in the same series.