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Agent skill

CSS Alpha Masking

by nirholas in nirholas/three.ws

Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image).

Apache-2.0Auto-check passedFrontend & Design

Install CSS Alpha Masking

skills CLI
$ npx skills add nirholas/three.ws --skill css-alpha-masking -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install nirholas/three.ws css-alpha-masking --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/nirholas/three.ws.git skills-src && mkdir -p .claude/skills && cp -r skills-src/third_party/designcode-agent-skills/agent-skills/web-design/css-alpha-masking .claude/skills/css-alpha-masking && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
css-alpha-masking
GitHub stars
226
Used in
1 other repo
Token cost
~445 tokens
SKILL.md length
151 words
Files
4
Skills in repo
165
Repo updated
First seen
Licence
Apache-2.0

At a glance

Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image).

  • Works in 3 steps: Confirm direction (horizontal or… → Provide the inline CSS snippet and any… → Offer small tweaks only (direction, stop…
  • Asked for alpha masks
  • SKILL.md covers Workflow, Usage checklist, Horizontal (left/right) fade and Vertical (top/bottom) fade, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

CSS Alpha Masking is an agent skill from nirholas/three.ws. Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image). Use when asked for alpha masks, fade edges, or CSS mask gradients.

Its SKILL.md is about 450 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files (for example `demo/PROMPT.md`).

It sits in Frontend & Design. The repository describes itself as: Open-source platform for 3D AI agents. Turn text or a photo into a rigged, animated GLB avatar, give it an LLM brain, memory and a wallet, and embed it anywhere with one web… The licence is Apache-2.0.

When your agent uses it

  • Asked for alpha masks
  • CSS mask gradients

Example prompts

  • “/css-alpha-masking”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. Confirm direction (horizontal or vertical) and fade stop percentages.
  2. Provide the inline CSS snippet and any needed class usage.
  3. Offer small tweaks only (direction, stop positions, colors).

What it can do on your machine

Read from SKILL.md and the folder at commit 238ef60. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are css).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

CSS Alpha Masking loads about 445 tokens when it runs. Until then it costs about 51 tokens; SKILL.md has 151 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~51
When it runs · the whole SKILL.md, loaded when a task matches
~445

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from nirholas/three.ws at commit 238ef60, republished under its Apache-2.0 licence (© nirholas). 151 words, ~445 tokens.

Download SKILL.mdSave it as .claude/skills/css-alpha-masking/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.
name
css-alpha-masking
description
Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image). Use when asked for alpha masks, fade edges, or CSS mask gradients.

CSS Alpha Masking Skill

Workflow

  1. Confirm direction (horizontal or vertical) and fade stop percentages.
  2. Provide the inline CSS snippet and any needed class usage.
  3. Offer small tweaks only (direction, stop positions, colors).

Usage checklist

  • Apply the mask styles directly on the element or in a CSS class.
  • Always include both mask-image and -webkit-mask-image for Safari.
  • Ensure the element has visible content; masks reveal/hide alpha only.

Horizontal (left/right) fade

css
/* Add this inline CSS to any element */
mask-image: linear-gradient(to right, transparent, black 15%, black 85%, transparent);
-webkit-mask-image: linear-gradient(to right, transparent, black 15%, black 85%, transparent);

Vertical (top/bottom) fade

css
/* Add this inline CSS to any element */
mask-image: linear-gradient(to bottom, transparent, black 15%, black 85%, transparent);
-webkit-mask-image: linear-gradient(to bottom, transparent, black 15%, black 85%, transparent);

Customization knobs

  • Direction: to right, to left, to bottom, to top.
  • Fade depth: adjust 15% and 85% stops.
  • Strength: change transparent to rgba(0,0,0,0.2) for softer fades.

Common pitfalls

  • Forgetting the -webkit-mask-image fallback in Safari.
  • Expecting masks to work on elements with overflow: hidden but no visible content behind.

Questions to ask when specs are missing

  • Which direction should the fade go?
  • How wide should the fade edges be?
  • Is this for images, text, or a container background?

© nirholas, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 3 other files in third_party/designcode-agent-skills/agent-skills/web-design/css-alpha-masking of nirholas/three.ws.

  • SKILL.md
  • demo/PROMPT.md
  • demo/index.html
  • demo/preview.jpg

Open the folder on GitHubat commit 238ef60

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in nirholas/three.ws, which our catalogue first saw on October 7, 2026.

Compare with similar skills

CSS Alpha Masking next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

CSS Alpha Masking compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
CSS Alpha Masking this skillnirholas/three.ws2261 repos~445Automated safety check: PassApache-2.0
Web Artifacts Builderanthropics/skills180k40 repos~769Automated safety check: PassApache-2.0
React Doctormakeplane/plane60k12 repos~657Automated safety check: PassAGPL-3.0
React Composition Patternsvercel-labs/openreview1.7k58 repos~721Automated safety check: PassMIT
Impeccablebestofjs/bestofjs3.1k27 repos~2.6kAutomated safety check: PassMIT
Figma Design System Builderwarpdotdev/warp65k2 repos~4.4kAutomated safety check: PassAGPL-3.0

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Categories

Questions about CSS Alpha Masking

What does CSS Alpha Masking do?

Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image). ws. Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image).

When should I use CSS Alpha Masking?

CSS Alpha Masking fits situations like: asked for alpha masks; CSS mask gradients.

How do I install CSS Alpha Masking in Claude Code?

Run `npx skills add nirholas/three.ws --skill css-alpha-masking -a claude-code`. Or copy the skill folder (third_party/designcode-agent-skills/agent-skills/web-design/css-alpha-masking in nirholas/three.ws) into .claude/skills/css-alpha-masking in your project. Claude Code loads it when a task matches its description.

How do I install CSS Alpha Masking in Codex?

Run `npx skills add nirholas/three.ws --skill css-alpha-masking -a codex`. Or copy the skill folder (third_party/designcode-agent-skills/agent-skills/web-design/css-alpha-masking in nirholas/three.ws) into .agents/skills/css-alpha-masking in your project. Codex loads it when a task matches its description.

Can I use CSS Alpha Masking in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add nirholas/three.ws --skill css-alpha-masking -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/css-alpha-masking, .gemini/skills/css-alpha-masking, .github/skills/css-alpha-masking and .opencode/skills/css-alpha-masking in your project.

What does CSS Alpha Masking need to run?

SKILL.md names no scripts, command-line tools or credentials: CSS Alpha Masking is instructions for the agent only.

Does CSS Alpha Masking access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is CSS Alpha Masking safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does CSS Alpha Masking use?

CSS Alpha Masking is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does CSS Alpha Masking use?

About 445 tokens (SKILL.md is roughly 1.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to CSS Alpha Masking?

Skills that share tags, products or a category with CSS Alpha Masking: Web Artifacts Builder (anthropics/skills, 180k stars), React Doctor (makeplane/plane, 60k stars), React Composition Patterns (vercel-labs/openreview, 1.7k stars) and Impeccable (bestofjs/bestofjs, 3.1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains CSS Alpha Masking?

nirholas (a GitHub user) maintains it in nirholas/three.ws, which has 226 GitHub stars. The repository holds 165 skills in this directory. The repository was last updated on October 7, 2026.

Source: nirholas/three.ws on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.