<button>Show Dialog</button>

<dialog>
  <h1>I am the dialog!</h1>
  <p>As of Chrome 122 my backdrop is light purple, because from that version on the <code>::backdrop</code> inherits any inheritable properties–including custom properties–from the <code>dialog</code> element.</p>
  <form method="dialog"><button>Close</button></form>
</dialog>

dialog {
  --border-color: #6300ff;
  --backdrop-color: #6300ff33; /* Could also use relative color syntax here :) */
}

::backdrop {
  background-color: var(--backdrop-color); /* This works as of Chrome 122 */
}

@layer reset {
  *,
  *:after,
  *:before {
    box-sizing: border-box;
  }

  html,
  body {
    margin: 0;
    padding: 0;
    background: white;
  }

  ul[class] {
    list-style: none;
  }

  label {
    cursor: pointer;
    max-width: max-content;
    user-select: none;
  }
}

@layer baselayout {
  html {
    margin: auto;
    line-height: 1.5;
    font-size: 24px;
    font-family: "Syne", sans-serif;
    min-height: 100%;
    background: white;
  }

  body {
    width: 100%;
    max-width: 120ch;
    margin: 0 auto;
    min-height: 100dvh;
    padding: 2em;
    display: grid;
    place-content: center;
  }

  footer {
    text-align: center;
    font-style: italic;
    margin-top: 2rem;
  }

  h1,
  h2,
  summary {
    font-family: "Anybody", sans-serif;

    text-decoration: underline;
    text-decoration-color: hsl(156deg 100% 50% / 50%);
    text-decoration-thickness: 0.2rem;
    text-decoration-style: wavy;
    text-decoration-skip-ink: none;
  }

  h2 {
    margin: 2em 0 0.5em 0;
    text-wrap: balance;
  }

  a {
    color: inherit;
  }

  button,
  input,
  textarea {
    font-family: inherit;
    font-size: inherit;
  }
}

@layer components {
  @layer dialog {
    dialog {
      --timing: 0.25s;
      border: 0.25em solid var(--border-color);
      transition: all var(--timing) ease,
        display var(--timing) ease allow-discrete;
      opacity: 0;
      max-width: 80ch;
      width: 90%;
      border-radius: 0.25em;

      &[open] {
        opacity: 1;

        @starting-style {
          opacity: 0;
        }
      }
    }
  }

  @layer button {
    button {
      padding: 0.2em 0.4em;
      border-width: 2px;
      border-radius: 0.25em;
      text-transform: uppercase;
    }
  }
}

@layer utilities {
  .float-right {
    float: right;
    margin-left: 0.5em;
  }
  .float-left {
    float: left;
    margin-right: 0.5em;
  }
  *:has(> .float-right, > .float-left) {
    display: flow-root;
  }

  .sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
  }
}

document.querySelector("button").addEventListener("click", (e) => {
  document.querySelector("dialog").showModal();
});