App Preview Craft

app-preview-craft — store screenshots, social cards and 3D device videos

Everything this skill makes is a page (stage/stage.html) posed by a theme and captured by headless Chrome: stills are screenshotted and finished by sharp, videos are rendered frame by frame and piped into ffmpeg. The same page powers the preview studio, so what the user sees there is exactly what the CLI exports.

0. Find the skill, set it up once

Paths below are relative to the directory holding this SKILL.md. Resolve it once and prefix commands with it — $SKILL means that directory throughout:

SKILL=/absolute/path/to/app-preview-craft        # the folder with SKILL.md, scripts/, stage/
# not sure where it was installed? (skill folders, then the Claude Code plugin cache)
find ./.claude/skills ./.agents/skills ./.goose/skills ~/.claude/skills ~/.agents/skills \
     ~/.gemini/skills ~/.config/goose/skills ~/.claude/plugins \
     -path '*app-preview-craft*/scripts/cli.mjs' 2>/dev/null | head -1

Then check the machine. --fix runs npm install inside the skill when packages are missing:

node "$SKILL/scripts/doctor.mjs" --fix

Doctor must end with Ready. A missing ffmpeg is only a warning (stills still work). If it reports no WebGL, 3D themes cannot render — say so rather than silently switching to flat themes.

Outputs go to the directory the user is working in (the shell's cwd) unless they name another folder with --out. Never write renders into $SKILL. Temp state lives in $TMPDIR/app-preview-craft/ and is removed after each run.

1. Workflow

1. Pick the category (the first CLI argument) from what the user asked for:

   Category	Makes	Default size
   app-store	A set: one screenshot per slide, per size, plus overview.png	iphone-6.9 1320×2868
   social-card	One card (or --all slides) for og/X/LinkedIn/Instagram/story	og 1200×630
   screen-video	2D motion from the screens alone; accepts screen recordings	reel 1080×1920
   device-video	three.js device showcase video	reel 1080×1920
   device-mockup	3D hero still, optionally transparent	mockup-landscape 2400×1600

2. Gather content. Screenshots (PNG/JPG/WebP) and/or recordings (MP4/MOV/WebM) from the user's project, one per slide, in order. Write the copy yourself unless the user supplied it (see §4). With no screens the bundled sample app "Tempo" is used — fine for showing themes, never for a deliverable.

3. Pick a theme. A theme the user names wins. For App Store sets, match the app's store category to the table in §3 and say which theme you chose and why. When the user is undecided, show them the options first:

   node "$SKILL/scripts/cli.mjs" gallery app-store        # → ./gallery-app-store.png
   

   Read the sheet back (so it renders for the user) and let them choose. The studio (§8) is the better answer when they want to browse and tweak visually.

4. Render.

   node "$SKILL/scripts/cli.mjs" app-store shots/01.png shots/02.png shots/03.png \
     --theme ledger \
     --title "Every euro, *accounted for*" --title "Budgets that *adapt*" --title "Private *by design*" \
     --subtitle "One-line benefit…" --subtitle "…" --subtitle "…" \
     --size iphone-6.9,ipad-13 --set palette.accent=auto
   

5. Inspect before you report. Read overview.png (sets), the still, or pull frames from a video (--frames 1,4,mid,end renders PNG frames instead of a video — cheap for checking motion). Look for clipped headlines, text over the device, a device covering decor, empty screens. Fix with --set/per-slide overrides and re-render.

6. Report the output paths, the theme and size, and — whenever a 3D device appears — that CREDITS.txt was written and that the CC-BY credit must travel with the images (§7).

2. Sizes

node "$SKILL/scripts/cli.mjs" list sizes --category app-store prints the table. Any WxH works too. Several at once: --size iphone-6.9,iphone-6.5,ipad-13.

• App Store Connect requires the 6.9" set (iphone-6.9) for iPhone apps and ipad-13 for iPad apps; other sizes are optional. PNG output is flattened (Apple rejects alpha).
• Tablet sizes automatically swap the phone for a flat tablet frame unless the theme is frameless. Give iPad screenshots for those slides when the app has them.
• App preview videos: --size app-preview (886×1920) or app-preview-ipad, 15–30 s, 30 fps. A silent stereo AAC track is added automatically (Connect expects audio).
• Google Play: play-phone, play-tablet, and play-feature (1024×500, social-card).

3. Themes

list themes --category <c> prints these with their layouts. Every category has ≥ 5.

app-store — each modelled on a popular app category

The themes borrow a mood, never a brand: no logos, names or artwork of those apps appear.

social-card

launch (aurora + tilted phone), spotlight (beam + mirror floor), pastel-fan (three fanned screens), bento (grid of screen crops), neon-grid (synthwave), editorial (paper, serif, duotone screen), duo (MacBook + phone — pass a desktop screen for the laptop).

screen-video (2D)

carousel, stack (cards flick away), scroll (long captures scroll inside the phone), zoom-tour (full-bleed Ken Burns to each slide's focus), wall (tilted wall of screens), store-preview (App Store preview style — use --size app-preview), grid-reveal.

device-video (3D)

turntable, orbit (camera arcs), float (loopable), rise (camera pushes in), flip (back → front reveal), trio (three models fan out), desk (MacBook lid opens, phone slides in beside it; both stand on scene.floor), spotlight (360° on a mirror), synthwave, keyframes (your own device and camera move, from motion.keys — see §5).

device-mockup (3D stills)

studio, noir, pedestal, levitate, lineup (every phone model), flatlay, desk-duo. Add --transparent for a cut-out PNG.

4. Copy

• Headline per slide: ≤ 6 words, a benefit not a feature. Wrap 1–2 words in *asterisks* to highlight them in the theme's style; " | " forces a line break.
• Subtitle: one short sentence. Kicker (optional): one word label above.
• First two slides carry the pitch — most shoppers never scroll further.
• Never invent ratings, download counts, awards or press quotes. Decor such as rating and laurels is for real figures the user gives you; ask when unsure.
• Don't name competitors or use Apple/Google trademarks in copy beyond what store guidelines allow.

5. Configuring anything

Resolution order, later wins: built-in base → layout defaults → theme (and its extends chain) → custom theme file → project config themeOverrides → CLI shortcuts → --set → per-slide theme.

• Shortcuts: --layout --device --finish --pose --font --body-font --bg --bg2 --bg3 --ink --sub --accent --accent2 --background --pattern --background-image --clean-status-bar --no-decor --duration --fps --speed --intro --outro.
• --set path=value reaches any theme key (repeatable). list options prints the documented paths with types and ranges. Values are coerced; JSON works for lists/objects: --set device.pose=5,-15,4 --set 'decor=[{"kind":"sparkles","count":8}]'.
• device.pose is x,y,z degrees. Themes stay inside roughly ±20° yaw and ±6° roll so the screen still reads at store-thumbnail size; steeper poses work but cost legibility.
• Colors accept auto = the most vivid color in the first screenshot: --accent auto.
• --device iphone-17-pro | iphone-17-pro-max | iphone-12-pro | galaxy-s21-ultra | macbook-pro-16 | flat[:phone|phone-android|tablet|browser] | frameless | none, or the id of the user's own model (§7).
• Layouts are interchangeable within a kind (list layouts): stills — hero-top, hero-bottom, tilt, duo, fan, split, big-type, callout, bento, laptop-phone, showcase, pedestal, lineup, flatlay; videos — carousel, stack, scroll, zoom-tour, wall, phone-swap, grid-reveal, turntable, orbit, float, rise, flip, trio, desk, spotlight, keyframes.
• Your own motion: the keyframes layout moves one 3D device and the camera through motion.keys, a list of { "at": 0..1, "x", "y", "size", "pose": [rx, ry, rz], "cam": { "yaw", "pitch", "dist" }, "ease" }. at is a fraction of the whole video; a value a key leaves out holds from the key before; the first key starts from the theme's own pose. Eases: linear inOutCubic inOutSine outCubic outQuart outBack inOutQuart outExpo. --theme keyframes --set 'motion.keys=[{"at":0,"y":1.4,"pose":[0,70,0]},{"at":0.3,"y":0.62,"pose":[4,-20,3],"ease":"outQuart"},{"at":1,"pose":[0,15,0],"cam":{"dist":0.9}}]'. No animation library is involved: every frame is a pure function of its time, which is what lets frames render out of order. Check a move with --frames 0,2,mid,end.

Custom themes are JSON (or .mjs) files with any subset of theme keys plus extends:

{ "extends": "app-store/ledger", "name": "Acme", "palette": { "accent": "#ff5a1f" },
  "type": { "display": "bricolage", "weight": 800 }, "device": { "finish": "#1c1f24" } }

Pass --theme path/to/acme.json, or drop it in ./.app-preview-craft/themes/ (or ~/.app-preview-craft/themes/) and use --theme acme. list themes shows custom ones.

Project config. node "$SKILL/scripts/cli.mjs" init app-store writes app-preview-craft.json; afterwards node "$SKILL/scripts/cli.mjs" (no arguments) renders it, and flags still override it. $SKILL/examples/app-preview-craft.json is a complete, working example: per-slide copy, decor and theme overrides, a custom theme file, a desktop screen, and a jobs list that renders an App Store set, a social card, a mockup and a video in one command. Paths in a config resolve relative to the config file.

Per-slide keys: screen, desktop (laptop display), title, subtitle, kicker, theme (overrides for that slide only), decor (replaces the theme's decor for that slide), focus: [x, y, zoom] (zoom-tour target), hold (seconds in a video), trim: [start, end] and at (which second of a recording a still uses), bigWord (big-type layout).

Decor items are {kind, x, y, scale, rotate, style, layer, delay, …} with x/y as page fractions and style one of glass | solid | light | dark | outline:

6. Screens and treatments

• sharp prepares every screenshot before Chrome starts: screen.cleanStatusBar (redraws a 9:41 / full-battery iOS status bar — phone-shaped captures only), tint + tintAmount, duotone: "#dark,#light", saturate, brightness, sharpen, and a pre-blurred backdrop for blur-shot backgrounds.
• On iPhone models the Dynamic Island is drawn as one merged black pill over the model's pill-and-camera cutouts, matching what iOS shows. Supply screenshots with the island area clear (any normal iOS capture is); cleanStatusBar keeps the time and icons either side.
• A capture taller than the display scrolls in videos (scroll theme) and shows its top in stills (screen.fit=top).
• Recordings are split into frames by ffmpeg at the output frame rate; in videos each recording's slide lasts as long as the clip (override with hold, cut with trim). Stills use one frame (at, default: the middle).
• Laptop displays letterbox a phone screenshot over a blurred copy unless the slide has a desktop screen. desktop takes a recording too. In the desk video the laptop keeps the last desktop given while later slides change the phone, so one web capture (or one recording, which plays on across those slides) on the first slide is enough.

7. 3D models and credits — required

The device models are CC-BY-4.0 (authors: Ranguel, MajdyModels, DatSketch, jackbaeten; see assets/CREDITS.md). Whenever a render shows one, the CLI writes CREDITS.txt beside the output and embeds the credit in video metadata and PNG EXIF. Tell the user the credit has to accompany published images (a line in the store description, the site footer, or the post). Never delete or edit CREDITS.txt to hide it. Flat and frameless themes use no models and write no credits.

scripts/models.mjs --from <folder> re-imports the source GLBs (WebP textures + meshopt geometry, credits read from each file's metadata).

The user's own 3D model

Any .glb works as a device, Draco and meshopt compressed files included — the decoders are WebAssembly and load only when a file needs them. Convert .gltf, .fbx, .obj or .usdz to GLB first. A model needs one thing said about it: which part is the display.

node "$SKILL/scripts/cli.mjs" inspect phone.glb        # materials, meshes, the guessed screen, credit found in the file
node "$SKILL/scripts/cli.mjs" device-mockup home.png --model phone.glb --set device.pose=0,0,0

• --model file.glb makes it the device. --model-screen <material> (or mesh:<name>) names the display when the guess is wrong or inspect reports low confidence; --model-rotate x,y,z (degrees) turns a model whose screen faces away or that lies on its side; --model-kind phone|laptop overrides sizing (default: by its proportions).

• Check with a front render before anything else: --set device.pose=0,0,0, then read the PNG. Screenshot showing, upright, facing you → done. Dark panel → wrong screen material. Back of the device → --model-rotate 0,180,0. Lying down → try 90,0,0 or -90,0,0.

• To keep it: put the GLB in ./.app-preview-craft/models/ (or ~/.app-preview-craft/models/ for every project) with a record beside it, <id>.json, and use --device <id>:

  { "name": "Pixel 9", "file": "pixel-9.glb", "screen": { "material": "Screen" },
    "rotate": [0, 180, 0], "hide": [{ "material": "Glass" }], "body": ["Frame"],
    "credit": { "title": "Pixel 9", "author": "…", "license": "CC-BY-4.0", "source": "https://…" } }
  

  hide removes cover glass that dims the display, body lists the materials --finish repaints, display: [w, h] overrides the screen shape (default: measured from the mesh), island: true draws the Dynamic Island. A project config takes the same records under "devices": { "<id>": { … } }. list devices shows what is installed.

• Credit: ask where the model came from. A downloaded model almost always needs its author credited (the record's credit; inspect shows what the file itself states). CREDITS.txt carries it, or a line saying no credit is on record — do not remove either.

8. The studio

node "$SKILL/scripts/cli.mjs" studio            # opens http://127.0.0.1:4747/studio/

A preview-first editor on localhost, run from the user's project folder: category tabs, the live previews (the same three.js stage the CLI captures), a theme dock, drag-and-drop screenshots/recordings, a Customize panel generated from the same schema as --set, export with progress, "Save as theme", "Save app-preview-craft.json" and "Copy command" (the exact CLI call). Uploads are saved to ./.app-preview-craft/uploads/; exports go to the folder the studio was started in. Suggest it when the user wants to explore looks; run it in the background and give them the URL.

The preview is the editor. Tools sit above it:

Text is edited in place. On stills, All slides / This slide decides whether a drag becomes a theme override or that slide's own theme. Lights, camera, pose, position, size, finish and glare change on the loaded scene (~1 ms, pixel-identical to a fresh load — the selftest checks it); anything else reloads the frame. ⌘Z / ⇧⌘Z undo and redo. On the keyframes theme the scrubber shows the keys: pause anywhere, pose the device or camera, and that pose becomes the key at the playhead. Dropping a .glb adds the user's own model (§7); when the display cannot be guessed, the studio asks them to click it.

Reading what the user did — the transcript

The studio writes everything done in it to the project, so you can follow along without being told:

node "$SKILL/scripts/cli.mjs" transcript              # where it stands now + the last 40 steps
node "$SKILL/scripts/cli.mjs" transcript --json --tail 200

• .app-preview-craft/studio/transcript.jsonl — one event per line, {n, t, type, text, …}. text is the step in words ("Turned iPhone 17 Pro — device.pose = 4, -18, 3"); the other fields are the same thing as data (path/value, changes, slide, scope, files). Types: session category theme size layout override override.reset preview.edit preview.decor keyframe slide.add slide.screen slide.move slide.remove slide.edit slide.text brand model.add model.update theme.save config.save export.start export.done export.fail undo redo.
• .app-preview-craft/studio/session.json — the current setup as a project config. Render exactly what they are looking at: cli.mjs --config .app-preview-craft/studio/session.json (add --size, --format, --out as needed). Its command field is the same thing as flags.

After the user says they are done in the studio, run transcript before rendering or answering questions about "what I changed". An undo line means the step before it no longer applies — trust session.json for the state, the event list for the story.

9. Useful commands

node "$SKILL/scripts/cli.mjs" --help
node "$SKILL/scripts/cli.mjs" list [categories|themes|sizes|devices|fonts|layouts|options]
node "$SKILL/scripts/cli.mjs" social-card shot.png --theme launch --size og,x-post,story --title "Meet *Acme*"
node "$SKILL/scripts/cli.mjs" device-video a.png b.png demo.mov --theme desk --duration 12 --format mp4
node "$SKILL/scripts/cli.mjs" screen-video flow.mp4 --theme store-preview --size app-preview
node "$SKILL/scripts/cli.mjs" device-mockup home.png --theme noir --transparent --size 3000x2000
node "$SKILL/scripts/cli.mjs" device-video … --frames 0.5,3,mid     # PNG frames to check motion
node "$SKILL/scripts/cli.mjs" app-store … --dry-run                 # print the resolved spec
node "$SKILL/scripts/cli.mjs" inspect model.glb                     # a 3D model's materials and likely screen (§7)
node "$SKILL/scripts/cli.mjs" transcript                            # what the user did in the studio (§8)
node "$SKILL/scripts/selftest.mjs" --quick                          # after changing scripts/ or stage/

Video formats: mp4 (H.264, BT.709, faststart), hevc, mov (ProRes 4444, keeps alpha with --transparent), webm (VP9, alpha), gif. Add music with --audio track.mp3 (faded out at the end). Rendering speed on an Apple-silicon GPU is roughly 15–20 frames per second at 1080p.

10. Troubleshooting