Playground death loop

[brunnerh]

This code (from a user question) will kill the playground:

<button class="shiny-cta">
  <span>Prøv Oss!</span>
</button>

<style>
  @import url("https://use.typekit.net/tzv3rms.css");

  :root {
      --shiny-cta-bg: #000000;
      --shiny-cta-bg-subtle: #1a1818;
      --shiny-cta-fg: #ffffff;
      --shiny-cta-highlight: #3772ff;
      --shiny-cta-highlight-subtle: #1a243e;
  }

  @property --gradient-angle {
      syntax: "<angle>";
      initial-value: 0deg;
      inherits: false;
  }

  @property --gradient-angle-offset {
      syntax: "<angle>";
      initial-value: 0deg;
      inherits: false;
  }

  @property --gradient-percent {
      syntax: "<percentage>";
      initial-value: 5%;
      inherits: false;
  }

  @property --gradient-shine {
      syntax: "<color>";
      initial-value: white;
      inherits: false;
  }

  .shiny-cta {
      --animation: gradient-angle linear infinite;
      --duration: 3s;
      --shadow-size: 2px;
      isolation: isolate;
      position: relative;
      overflow: hidden;
      cursor: pointer;
      outline-offset: 4px;
      padding: 1.25rem 2.5rem;
      font-family: inherit;
      font-size: 1.125rem;
      line-height: 1.2;
      border: 1px solid transparent;
      border-radius: 360px;
      color: var(--shiny-cta-fg);
      background: linear-gradient(var(--shiny-cta-bg), var(--shiny-cta-bg))
          padding-box,
      conic-gradient(
          from calc(var(--gradient-angle) - var(--gradient-angle-offset)),
          transparent,
          var(--shiny-cta-highlight) var(--gradient-percent),
          var(--gradient-shine) calc(var(--gradient-percent) * 2),
          var(--shiny-cta-highlight) calc(var(--gradient-percent) * 3),
          transparent calc(var(--gradient-percent) * 4)
      )
      border-box;
      box-shadow: inset 0 0 0 1px var(--shiny-cta-bg-subtle);
  }

  .shiny-cta::before,
  .shiny-cta::after,
  .shiny-cta span::before {
      content: "";
      pointer-events: none;
      position: absolute;
      inset-inline-start: 50%;
      inset-block-start: 50%;
      translate: -50% -50%;
      z-index: -1;
  } 

  .shiny-cta:active {
      translate: 0 1px;
  }

  .shiny-cta::before {
      --size: calc(100% - var(--shadow-size) * 3);
      --position: 2px;
      --space: calc(var(--position) * 2);
      width: var(--size);
      height: var(--size);
      background: radial-gradient(
          circle at var(--position) var(--position),
          white calc(var(--position) / 4),
          transparent 0
      )
      padding-box;
      background-size: var(--space) var(--space);
      background-repeat: space;
      mask-image: conic-gradient(
          from calc(var(--gradient-angle) + 45deg),
          black,
          transparent 10% 90%,
          black
      );
      border-radius: inherit;
      opacity: 0.4;
      z-index: -1;
  }

  .shiny-cta::after {
      --animation: shimmer linear infinite;
      width: 100%;
      aspect-ratio: 1;
      background: linear-gradient(
          -50deg,
          transparent,
          var(--shiny-cta-highlight),
          transparent
      );
      mask-image: radial-gradient(circle at bottom, transparent 40%, black);
      opacity: 0.6;
  }

  .shiny-cta span {
      z-index: 1;
  }

  .shiny-cta span::before {
      --size: calc(100% + 1rem);
      width: var(--size);
      height: var(--size);
      box-shadow: inset 0 -1ex 2rem 4px var(--shiny-cta-highlight);
      opacity: 0;
  }

  .shiny-cta {
      --transition: 800ms cubic-bezier(0.25, 1, 0.5, 1);
      transition: var(--transition);
      transition-property: --gradient-angle-offset, --gradient-percent,
      --gradient-shine;
  }

  .shiny-cta,
  .shiny-cta::before,
  .shiny-cta::after {
      animation: var(--animation) var(--duration),
      var(--animation) calc(var(--duration) / 0.4) reverse paused;
      animation-composition: add;
  }

  .shiny-cta span::before {
      transition: opacity var(--transition);
      animation: calc(var(--duration) * 1.5) breathe linear infinite;
  }

  .shiny-cta:is(:hover, :focus-visible) {
      --gradient-percent: 20%;
      --gradient-angle-offset: 95deg;
      --gradient-shine: var(--shiny-cta-highlight-subtle);
  }

  .shiny-cta:is(:hover, :focus-visible),
  .shiny-cta:is(:hover, :focus-visible)::before,
  .shiny-cta:is(:hover, :focus-visible)::after {
      animation-play-state: running;
  }

  .shiny-cta:is(:hover, :focus-visible) span::before {
      opacity: 1;
  }

  @keyframes gradient-angle {
      to {
          --gradient-angle: 360deg;
      }
  }

  @keyframes shimmer {
      to {
          rotate: 360deg;
      }
  }

  @keyframes breathe {
      from,
      to {
          scale: 1;
      }
      50% {
          scale: 1.2;
      }
  }
</style>

[brunnerh]

Found another thing that sends it spinning - tried to add :global() around the input selector:

<label>
	<input type="checkbox" />
	<span>hi</span>
</label>

<style>
	label:has(input) span {
		color:red
	}
</style>

Playground

I.e. start typing :global in front of input.

[dummdidumm]

I started debugging this and it seems neither the workers nor the editor syntax highlighting is the problem.

[dummdidumm]

So it seems the AST output is the culprit. Trying to find out why now.

Edit: May actually be a bug within Svelte. The metadata object on complex selectors inside pseudo classes is not removed for some reason, seems like zimmerframe's walk doesn't reach it. No idea why.

[andirady]

Found another thing that sends it spinning - tried to add :global() around the input selector:

<label>
	<input type="checkbox" />
	<span>hi</span>
</label>

<style>
	label:has(input) span {
		color:red
	}
</style>

Playground

I.e. start typing :global in front of input.

The playground will slow down whenever you introduce :global. It's worse if you typed :global(body).