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CSS

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HTML 

              
                <div class="topbanner">
  This is just a top banner for the fun of it.
</div>
<div class="header-container">
  <header>
    <div class="container">
      <div class="branding">
        <h1>Sticky header stuffs</h1>
      </div>
      <nav>
        <ul>
          <li><a href="#" class="active" aria-current="page">Home</a></li>
          <li><a href="#">Oh snap</a></li>
          <li><a href="#">About us</a></li>
          <li><a href="#">Contact</a></li>
        </ul>
      </nav>
    </div>
  </header>
</div>
<div class="grid">
  <main>
    <h1>This is the title of my main content</h1>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras convallis sodales erat vel accumsan. Nam eget massa nec sem vulputate ullamcorper vel quis justo. Duis rhoncus tempor tempus. Nulla facilisi. Maecenas nulla ante, lacinia ac consectetur non, aliquet sollicitudin libero. Quisque congue odio sodales dui fermentum ac laoreet mauris eleifend. Nulla facilisi. Phasellus vel erat a ante pharetra pharetra.</p>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras convallis sodales erat vel accumsan. Nam eget massa nec sem vulputate ullamcorper vel quis justo. Duis rhoncus tempor tempus. Nulla facilisi. Maecenas nulla ante, lacinia ac consectetur non, aliquet sollicitudin libero. Quisque congue odio sodales dui fermentum ac laoreet mauris eleifend. Nulla facilisi. Phasellus vel erat a ante pharetra pharetra.</p>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras convallis sodales erat vel accumsan. Nam eget massa nec sem vulputate ullamcorper vel quis justo. Duis rhoncus tempor tempus. Nulla facilisi. Maecenas nulla ante, lacinia ac consectetur non, aliquet sollicitudin libero. Quisque congue odio sodales dui fermentum ac laoreet mauris eleifend. Nulla facilisi. Phasellus vel erat a ante pharetra pharetra.</p>
    <p>
      Donec fringilla sem at eros vulputate tempus. Maecenas interdum leo a tortor lobortis in hendrerit est pellentesque. Vestibulum non leo et nisi sollicitudin rutrum. Aliquam tristique dui tempor sapien molestie mollis. Integer viverra faucibus nulla ut posuere. Sed quis dui dictum tortor imperdiet imperdiet ut scelerisque augue. Aenean sit amet libero sit amet metus pulvinar viverra et id tortor. Nulla iaculis bibendum nisi, quis elementum risus tempus et. Nullam rutrum, dolor id vulputate feugiat, lectus tortor auctor odio, et lacinia eros neque quis neque. Praesent nibh erat, varius porttitor cursus a, condimentum vel eros. Quisque odio urna, elementum a consequat id, facilisis eget mi. Praesent imperdiet congue velit, non tempus mi sollicitudin eu. Duis vitae nisi leo, ut ultrices leo. Aliquam dolor sapien, cursus suscipit fringilla et, lacinia et ligula. Proin eu lacus leo, at accumsan nisi. Nulla facilisi. Proin vehicula mi nec augue semper eleifend. Aliquam tempus vulputate quam at malesuada. Nulla a lacus sit amet urna varius cursus. Aliquam a nunc sapien. </p>
    <div class="banner">
      <h2>This is an awesome banner</h2>
      <p>Depending on the container, this will adjust its font-size and paddings to fit perfectly</p>
    </div>
  </main>
  <aside>
    <ul>
      <li>Lorem ipsum dolor sit amet</li>
      <li>lacinia ac consectetur non</li>
      <li>Phasellus vel erat a ante</li>
      <li> Nulla facilisi</li>
      <li>ac consectetur non</li>
    </ul>
    <div class="banner">
      <h2>This is an awesome banner</h2>
      <p>Depending on the container, this will adjust its font-size and paddings to fit perfectly</p>
    </div>
  </aside>
</div>
<div class="warning">This is a demo for state queries, use Chrome Canary and enable the experimental web platform features</div>
!

CSS 

              
                @import url("https://fonts.googleapis.com/css2?family=Open+Sans:wdth@75..100&family=Oswald:wght@600&display=swap");
@layer presentation, defaultgrid, layout, demo;

@layer demo {
  .header-container {
    width: 100%;
    position: sticky;
    top: 0;
    @supports (container-type: scroll-state) {
      container-type: scroll-state;
      header {
        transition: box-shadow 0.5s ease-out;
        h1 {
          transition: font-size 0.5s;
        }
        @container scroll-state(stuck: top) {
          box-shadow: rgba(0, 0, 0, 0.6) 0px 12px 28px 0px,
            rgba(0, 0, 0, 0.1) 0px 2px 4px 0px,
            rgba(255, 255, 255, 0.05) 0px 0px 0px 1px inset;
          h1 {
            font-size: 1.5rem;
          }
        }
      }
    }
  }
}

@layer layout {
  /*   Set container type */
  .grid > * {
    container-type: inline-size;
  }

  /* Style banner with cq units */
  .banner {
    padding: 3cqmax;
    background: #49416d;
    color: #b3f2dd;
    font-size: clamp(1rem, 2cqi + 0.5rem, 1.5rem);
    border-radius: 0.5rem;
    box-shadow: rgba(50, 50, 93, 0.25) 0px 6px 12px -2px,
      rgba(0, 0, 0, 0.3) 0px 3px 7px -3px;
    text-shadow: -1px -1px 1px rgba(255, 255, 255, 0.2),
      1px 1px 1px rgba(0, 0, 0, 0.6);
  }

  .banner h2 {
    font-size: clamp(1.3rem, 3cqi + 0.5rem, 2.4rem);
    margin: 0 0 1cqi;
  }

  /* Set container name for aside */
  aside {
    container-name: aside;
  }

  /* change the bgcolor when in the sidebar */
  @container aside (min-inline-size: 100px) {
    .banner {
      background-color: #a882dd;
      color: #111;
      text-shadow: none;
    }
  }
  .topbanner {
    background: salmon;
    color: white;
    width: 100%;
    padding: 1.2rem;
    text-align: center;
  }
}

@layer defaultgrid {
  .grid {
    display: grid;
    inline-size: 100%;
    min-block-size: 100dvb;
    gap: 3vmin;
    background: #e0efde;
    overflow: hidden;
    > * {
      padding: 1.5rem;
    }
    @media screen and (min-width: 768px) {
      grid-template-columns: 3fr 2fr;
    }
  }
  aside {
    background: #e08d79;
  }

  .banner p {
    margin: 0;
  }
}

@layer presentation {
  :root {
    --color-cerulean: #0081a7;
    --color-lightest: #fff;
    --color-orange: #fed9b7;
    --color-yellow: #fdfcdc;
    --color-verdigris: #00afb9;
    --color-cerulean: #0081a7;
    --color-lightest: #fff;
    --bg-slider: #161032;
  }

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

  body {
    margin: 0;
    padding: 0;
    font-family: "Open Sans", sans-serif;
    font-size: 1.1rem;
    line-height: 1.55;
    color: #49416d;
    min-block-size: 100dvb;
    place-content: center;
    place-items: center;
    background: #d3bdb0;
  }

  h1 {
    font-size: clamp(2rem, 5cqi + 0.5rem, 3rem);
    text-shadow: -1px -1px 1px rgba(255, 255, 255, 0.2),
      1px 1px 1px rgba(0, 0, 0, 0.6);
  }

  h1,
  h2 {
    font-family: "Oswald", sans-serif;
    font-weight: 600;
  }

  header {
    padding-block: 24px;
    background: #0081a7;

    width: 100%;
    .container {
      display: flex;
      flex-direction: column;
      align-items: center;
      padding-inline: 1.5rem;
      @media screen and (min-width: 768px) {
        flex-direction: row;
        justify-content: space-between;
        gap: 50px;
      }
    }
  }
  .branding {
    font-family: "Electrolize", sans-serif;
    display: flex;
    align-items: center;
    gap: 20px;
    color: var(--color-orange);
    & h1 {
      margin: 0;
      font-size: 1.6rem;
      @media screen and (min-width: 500px) {
        font-size: 2rem;
      }
    }
  }

  nav ul {
    display: flex;
    gap: 15px;
    margin-block: 15px 0;
    margin-inline: 0;
    padding: 0;
    list-style: none;
    font-size: 1rem;
    @media screen and (min-width: 1000px) {
      margin-block-start: 0;
      font-size: 1.4rem;
    }
  }

  a {
    color: var(--color-orange);
    text-decoration: none;
    transition: color 0.24s;
    &:is(:hover, :focus) {
      color: var(--color-lightest);
    }
    &.active {
      color: var(--color-lightest);
      text-decoration: underline;
    }
  }
}

.warning {
  position: fixed;
  top: 0;
  left: 0;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 1rem;
  color: black;
  background: yellow;
  padding: 10px;
  z-index: 10;
  @supports (container-type: scroll-state) {
    display: none;
  }
}
!

JS
!
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