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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

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JavaScript

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HTML 

              
                <section>

   <aside class="countdown">   

      <!-- define here the time needed to 
           read the article (in minutes).
           
           If you set <n> minutes you will see
           <n-1> mins and 59 seconds in the
           fixed bar.
      -->
      <style>
         @property --mm {
           syntax: '<integer>';
           initial-value: 24;
           inherits: true;
         }
      </style>

      <div>
         <svg viewBox="0 0 24 24"
              xmlns="http://www.w3.org/2000/svg">
            <circle cx="12" cy="12" r="11" />
            <path d="M12 12V6" id="hours" />
            <path d="M12 12V4" id="minutes" />
         </svg>
      </div>
      <div class="countdown__wrapper">
         <div class="countdown__display 
                     countdown__display--mm">
            <span>min</span>      
         </div>
         <div class="countdown__display 
                     countdown__display--ss">
            <span>sec</span>
         </div>
      </div>     
   </aside>



   <main id="top" tabindex="-1">

      <h1>Remaining reading time on scroll <br /><small>(in CSS)</small></h1>


      <div class="warning scroll">
         ⚠️ Your browser does not support Scroll-driven Animations. Please try Chrome 115+ with the “Experimental Web Platform Features” flag enabled.
      </div>

      <div class="warning motion">
         ⚠️ You set reduced motion preference, seconds are not available.
      </div>
      
      <div class="warning houdini">
         ⚠️ Your browser does not support Houdini APIs
      </div>
      
      
      <p>
         <strong>An example of scroll-driven animations made with just CSS!</strong> Scroll down the page and see how the reading time changes. Try to also change the initial value of the <code>--mm</code> variable (see the html panel on Codepen)</p> 
      
      <p>Too many updates on screen? Set <code>prefers-reduced-motion</code> to <code>reduced</code> on your system settings and show only the remaining minutes.
      </p>
      
      <hr />
      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>


      <h2>Lorem ipsum sit dolor amet</h2>
      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>

      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>


      <h2>Lorem ipsum sit dolor amet</h2>

      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>

      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>

      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>

      <p>
         Lorem ipsum dolor sit amet, consectetur 
         adipisicing elit. Tempora voluptatem, ex 
         ab ullam eaque perspiciatis nesciunt nobis 
         debitis dolorem quia iusto quam quod quasi 
         incidunt ipsa dolores facere facilis at.
         Sit consectetur possimus totam, quis 
         consequuntur doloremque exercitationem, 
         incidunt, vitae qui quidem magnam distinctio 
         nobis. Sapiente officia eaque, eum amet, 
         iusto ut exercitationem hic ad repellendus 
         nulla aut id. Expedita!
         Veniam sequi quia sit autem quam optio 
         quibusdam pariatur! Ipsa quo libero cumque. 
         Consectetur ipsam, asperiores tenetur id 
         libero, omnis doloremque a maiores dolor 
         dicta nam suscipit expedita eligendi. 
         Distinctio.
         Quaerat nemo recusandae nihil minus quae 
         provident dolore totam repudiandae voluptatem 
         assumenda eum, eligendi perspiciatis deserunt 
         unde. Magni vel, at error dignissimos 
         quibusdam rem commodi, libero fugit voluptatum 
         sit nisi!
         Accusamus facere saepe tempora repudiandae 
         pariatur temporibus veniam, asperiores eum 
         sunt aperiam expedita, dolores ullam ad unde 
         cumque rem, distinctio ipsam inventore 
         exercitationem ab facilis vero quasi! Placeat, 
         modi consequuntur!
      </p>

      <p>
         <a href="#top">Scroll to top</a>
      </p>

   </main>

</section>
!

CSS 

              
                
/* relevant CSS */

@property --ss {
  syntax: "<integer>";
  initial-value: 0;
  inherits: true;
}

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

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


/* --mm is defined in the HTML panel */

:root {
   --angle_mm: calc(6deg  * (var(--mm) + (var(--ss) / 60)));
   --angle_hh: calc(.5deg * var(--mm));
   
   animation: 
      mins steps(var(--mm), start) forwards,
      secs linear var(--mm) forwards,
      clock linear forwards;
   animation-timeline: scroll();
}


/* digital clock */

.countdown__display--mm {
   counter-reset: mm var(--mm);
   &::before {
      content: counter(mm, decimal-leading-zero);
   }
}

.countdown__display--ss {
   counter-reset: ss var(--ss);
   &::before {
      content: counter(ss, decimal-leading-zero);
   }
}

@media (prefers-reduced-motion: reduce) {
   .countdown__display--ss {
      display: none;
   }
}

@keyframes mins { to { --mm:0 } }
@keyframes secs { to { --ss:0 } from { --ss:59 } }


/* Analogic clock */

svg {
   display: block;
   inline-size: 3rem;
   margin: 0 auto;
   aspect-ratio: 1;
   fill: none;
   stroke: var(--color);  
   stroke-linecap: round;
}

#minutes {
   transform-origin: 50% 50%;
   transform: rotateZ(var(--angle_mm));
}

#hours {
   transform-origin: 50% 50%;
   transform: rotateZ(var(--angle_hh));
}


@keyframes clock { to { --angle_mm: 0deg } }

/* End of relevant CSS. */














/**  Not relevant for the core functionality **/


*, *::before, *::after {
  box-sizing: border-box;
  font-weight: 300;
}

html {
  scroll-behavior: smooth;
  padding: 0 0 2rem 0;
  margin: 0;
}

main {
  padding: 5rem var(--gap) 0;
  font: 300 1.2rem/1.9 Montserrat;
}

@media (min-width: 40rem) {
  main {
    padding-block-start: 0;
    margin-inline-end: 20%;
  }
}

main a {
  color: var(--color);
}
main p {
  margin-block-start: 3rem;
}
main h2 {
  text-align: left;
  font-size: 2.4rem;
  margin-block-start: 3rem;
}

h1 {
  font: 700 clamp(1.4rem, 1.4rem + 4vw, 5rem) "Hachi Maru Pop";
  color: var(--color);
  text-align: center;
  margin: 0;
  padding: 2rem 1rem 1rem;
}

small {
   font-size: 65%;
}

strong {
   color: var(--color);
   font-weight: 500;
}

code {
   font:inherit;
   font-style: italic;
   background: var(--color);
   color: #fff;
   padding: .25rem;
   border-radius: 5px;
   
}

@media (min-width: 40rem) {
  h1 {
    margin-block-start: 0;
  }
}

h2 {
  color: var(--color);
  text-align: center;
  margin: 1rem 0 0;
  font: 1.5rem "Hachi Maru Pop";
}

@media (max-width: 40rem) {
  h2 {
    margin: 0;
  }
}



:root {
  --gap: 1rem;
  --color: #689;
}

.countdown {
  position: fixed;
  padding: var(--gap);
  inset: 0 0 0 80%;
  background: #e6edf3;
}

@media (max-width: 39.99rem) {
  .countdown {
    display: flex;
    align-items: center;
    inset: 0 0 auto 0;
    justify-content: space-between;
  }
}

.countdown__wrapper {
  position: relative;
  display: flex;
  flex-flow: row wrap;
  flex: 1 1 auto;
  justify-content: flex-end;
  color: yellowgreen;
  gap: var(--gap);
}

@media (min-width: 40rem) {
  .countdown__wrapper {
    justify-content: center;
    padding: var(--gap);
  }
   
   svg {
      margin-block: 1rem 2rem;
   }
}

.countdown span {
  font: 66% "Hachi Maru Pop";
  color: var(--color);
}

.countdown__display {
  display: flex;
  align-items: center;
  flex-flow: column nowrap;
  font: 1.2rem Montserrat;
  font-weight: bold;
  animation-timeline: scroll;
}

@media (min-width: 40rem) {
  .countdown__display {
    min-inline-size: 70%;
    font-size: 2rem;
  }
}


.warning { 
   display: none;
   padding: 2rem;
   margin:  0 2rem 2rem 2rem;
   background: #ebeca9;
}

@media (prefers-reduced-motion: reduce) {
   .motion {
      display: block;
   }
}

@supports (not (animation-timeline: scroll())) {
   .scroll { 
      display: block;
   }
}

@supports not (background: paint(something))  {
  .houdini {
    display: block;
  }
}
!

JS 

              
                /* 
are you looking for JS? 
*/
!
999px

Console