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Vertical video design

Skill portel-dev/skills/skills/vertical-video-design

Official skills repository for Portel Photon

Install

npx -y skills add portel-dev/skills --skill vertical-video-design

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

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What its author says it does

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Platform-aware design rules for vertical video (Reels, Shorts, TikTok, LinkedIn mobile). Covers safe zones, caption sizing/placement, aspect ratios, thumb-stopper hooks, effects that survive mobile compression, and per-platform cheatsheets. Use when building 9:16 / 4:5 / 1:1 video for social media - any time you need to decide where to place text, how big captions should be, what aspect ratio to export, or which effects survive mobile playback.

SKILL.md

3.7 KB, 821 tokens by cl100k_base, as published. Nobody here has run it

Vertical Video Design

Rules for designing vertical video that survives mobile platform chrome, auto-play muted, and small-screen compression.

Core principle

The middle 70% is yours. The outer 30% belongs to the platform. Every vertical platform overlays its own UI on your video - captions, like/share buttons, handle + description, progress bar. If your content lives in that zone, it gets covered.

When to use

Invoke this skill when:

Designing any 9:16, 4:5, or 1:1 video for TikTok, Instagram Reels, YouTube Shorts, LinkedIn, Facebook Reels
Deciding where to place captions, headers, CTAs, or branding
Building Remotion compositions for vertical output
Choosing aspect ratio for a new video project
Reviewing why a video "looks cut off on mobile" or "the caption covers my face"

Quick reference

For the actual rules, load the relevant file:

rules/safe-zones.md - Per-platform exclusion zones. What pixels get covered by the platform's own UI. Start here for every layout.
rules/captions.md - Caption sizing, font, placement, timing, max chars per line. How to make burned-in subtitles readable on small screens.
rules/hooks.md - First-second rules for muted autoplay. Why text hooks fail and what works instead.
rules/effects.md - What survives mobile H.264 compression and what falls apart. Fine details, gradients, motion blur, etc.
rules/aspect-ratios.md - When to pick 9:16 vs 4:5 vs 1:1. Cross-posting strategies.
rules/platform-cheatsheet.md - One-page table: dimensions, max duration, safe zone px, file size limits per platform.

The 60-second checklist

Before exporting any vertical video, verify:

Safe zone respected - no critical content in top 12% or bottom 20% of the frame
Captions burn-in - text is large enough to read at phone size, placed in the safe middle
Opens with motion - first frame is not a static title card (muted autoplay will skip it)
Subject centered or 2/3 rule - not cropped off by a different-aspect platform resize
Aspect locked - exporting 9:16 (1080x1920) for TikTok/Reels/Shorts, or 4:5 (1080x1350) for LinkedIn feed video
Audio normalized - watching muted is default, but audio matters when it plays; use dynaudnorm to even out levels
Thumbnail-safe first frame - many platforms use frame 0 as the thumbnail; make it compelling

Common mistakes

Mistake	Why it's bad	Fix
Captions at very bottom	Platform progress bar covers them	Move captions to bottom third, not last 10%
Logo/branding at top-left	Platform handle + description overlays this area	Use top 0-5% only for subtle branding, or center-top
Small 24px text	Unreadable on phone screens	Minimum 36px for captions, 48+ preferred
Static opening	Muted autoplay doesn't catch attention	Start with motion: cursor, zoom, object moving
Single wide text line	Overflows safe zone horizontally	Max 30-35 chars per line, wrap to 2-3 lines
Exporting at 720p	Platforms re-encode; start sharp	Export 1080p+ always; platforms downscale better than upscale

Keep looking

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