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Animation On Scroll

Meng ToCommunityCreated by Meng To

  • Skill
  • Tool integration
  • Software development
  • MIT
  • No issues found
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From the author

Create an on-scroll animation trigger using IntersectionObserver with Tailwind-friendly animation classes and keyframes. Use when asked for scroll-reveal, animate-on-scroll, or sequencing element animations when they enter the viewport.
— the description by Meng To

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured workflow for adding scroll-reveal animations to web elements. It utilizes the IntersectionObserver API to detect when elements enter the viewport and triggers CSS keyframe animations. The approach is designed to integrate seamlessly with Tailwind CSS by leveraging arbitrary value syntax for animation properties, allowing for highly customizable motion effects like fades, slides, and blurs.

What it does

  • Provides a reusable JavaScript snippet to observe element visibility.
  • Defines CSS keyframes for smooth entrance animations.
  • Offers a method to apply animations using Tailwind CSS classes.
  • Includes configuration options for animation timing and trigger sensitivity.
  • Supports both one-time reveals and repeatable animations.

When to use it

  • When you need elements to animate as the user scrolls down the page.
  • When implementing scroll-reveal effects for landing pages or portfolios.
  • When you want to sequence animations for better visual engagement.
  • When you need a lightweight, dependency-free solution for scroll-based motion.

Advantages

  • Lightweight implementation using native browser APIs.
  • Highly compatible with Tailwind CSS utility classes.
  • Easy to customize animation duration, delay, and motion style.
  • Flexible trigger points via threshold and rootMargin adjustments.

Usage examples

“How do I make my hero section fade in when the user scrolls to it?”
The agent provides the keyframe CSS, the IntersectionObserver script, and the specific Tailwind class to add to the hero div.
“Can I make the animation repeat every time I scroll back to the element?”
The agent instructs you to set the 'once' variable to 'false' within the provided JavaScript snippet.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/mengto/animation-on-scroll/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip animation-on-scroll.zip -d .agents/skills

Documentation by Meng To

Animation On Scroll Skill

Workflow

  1. Confirm animation style, timing, and whether animations should run once or repeat.

  2. Provide the keyframes + JS observer snippet and the exact Tailwind class to apply.

  3. Offer focused tweaks only (threshold, rootMargin, duration, delay, transform/blur values).

Usage checklist

  • Insert the JS snippet in the <head> after the keyframes.

  • Add the animation class and animate-on-scroll to elements.

  • Ensure your keyframes name matches the Tailwind animation reference.

IntersectionObserver trigger

<script>
  /*
    Sequence animation on scroll when visible. Requires Animation Keyframe. Usage:

    1) Insert this code in the <head> along with the Animation Keyframe code.

    2) Add to Tailwind Classes: [animation:animationIn_0.8s_ease-out_0.1s_both] animate-on-scroll
  */
  (function () {
    // Inject CSS for paused/running states
    const style = document.createElement("style");
    style.textContent = `
      /* Default: paused */
      .animate-on-scroll { animation-play-state: paused !important; }
      /* Activated by JS */
      .animate-on-scroll.animate { animation-play-state: running !important; }
    `;
    document.head.appendChild(style);

    const once = true;

    if (!window.__inViewIO) {
      window.__inViewIO = new IntersectionObserver((entries) => {
        entries.forEach((entry) => {
          if (entry.isIntersecting) {
            entry.target.classList.add("animate");
            if (once) window.__inViewIO.unobserve(entry.target);
          }
        });
      }, { threshold: 0.2, rootMargin: "0px 0px -10% 0px" });
    }

    window.initInViewAnimations = function (selector = ".animate-on-scroll") {
      document.querySelectorAll(selector).forEach((el) => {
        window.__inViewIO.observe(el); // observing twice is a no-op
      });
    };

    document.addEventListener("DOMContentLoaded", () => initInViewAnimations());
  })();
</script>

Keyframes

<style>
  /*
    Sequence animation intro. Usage:

    1) Insert this code in the <head>

    2) Add to Tailwind Classes: [animation:animationIn_0.8s_ease-out_0.1s_both]
  */
  @keyframes animationIn {
    0% {
      opacity: 0;
      transform: translateY(30px);
      filter: blur(8px);
    }

    100% {
      opacity: 1;
      transform: translateY(0);
      filter: blur(0px);
    }
  }
</style>

Tailwind example

<div class="animate-on-scroll [animation:animationIn_0.8s_ease-out_0.1s_both]">
  ...
</div>

Customization knobs

  • Trigger: adjust threshold and rootMargin for earlier/later reveals.

  • Repeat: set once = false to allow replays when re-entering.

  • Motion: tweak translateY and blur in keyframes.

  • Timing: change duration and delay in the Tailwind animation value.

Common pitfalls

  • Forgetting to include the keyframes before the JS snippet.

  • Using a different keyframe name than in the Tailwind animation.

  • Animations not running because the element is already in view before observer init.

Questions to ask when specs are missing

  • Should animations run once or every time the element re-enters?

  • How far before entering the viewport should they start?

  • What motion style (fade, slide, blur, scale) do you want?

Files

LICENSE

MIT License

Copyright (c) 2026 Meng To

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by
Meng To
Publisher
Meng To (Community)
Source
MengTo/Skills · agent-skills/web-design/animation-on-scroll · commit 5ea1661
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced

AutoGineer is not affiliated with or endorsed by Meng To or Meng To.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download animation-on-scroll.zip