Grain Overlay

<!--
  Grain Overlay — animated film grain texture.

  Usage: paste this snippet into your composition's HTML.
  The overlay covers the full viewport with pointer-events: none
  so it sits on top of all content without blocking interaction.

  Customize:
  - opacity: adjust .grain-texture opacity (default 0.15)
  - speed: change animation duration (default 0.5s)
  - texture: swap the background URL for a different pattern
  - z-index: adjust #grain-overlay z-index to layer correctly
-->

<div
  id="grain-overlay"
  style="
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 100;
  "
>
  <div class="grain-texture"></div>
</div>

<style>
  @keyframes hf-grain-noise {
    0%,
    100% {
      transform: translate(0, 0);
    }
    10% {
      transform: translate(-5%, -5%);
    }
    20% {
      transform: translate(-10%, 5%);
    }
    30% {
      transform: translate(5%, -10%);
    }
    40% {
      transform: translate(-5%, 15%);
    }
    50% {
      transform: translate(-10%, 5%);
    }
    60% {
      transform: translate(15%, 0);
    }
    70% {
      transform: translate(0, 10%);
    }
    80% {
      transform: translate(-15%, 0);
    }
    90% {
      transform: translate(10%, 5%);
    }
  }

  #grain-overlay .grain-texture {
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
    opacity: 0.15;
    animation: hf-grain-noise 0.5s steps(1) infinite;
  }
</style>