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HTML

              
                <div class="no-support" data-support="css-trig-fns"><p>🚨 Your browser does not support the CSS Trigonometric Functions. Therefore, this demo will not work properly. Please try Safari 15.4, Firefox 108, or Chrome 111.</p></div>

<form data-has-support="at-property" method="">
  <label for="enable_animation">
    <input type="checkbox" name="enable_animation" id="enable_animation" checked />
    Auto-rotate
  </label>
  <label for="show_debug">
    <input type="checkbox" name="show_debug" id="show_debug" />
    Show Debug Lines
  </label>
</form>

<div class="wrapper">
  <div id="visual" data-countchildren>
    <span class="dot"></span>
    <span class="dot"></span>
    <span class="dot"></span>
    <span class="dot"></span>
    <span class="dot"></span>
  </div>
</div>

<div id="controls" data-show-when-has-support="css-trig-fns">
  <button data-trigger="add">Add dot</button>
  <button data-trigger="remove">Remove dot</button>
</div>

<footer>
  <p>Demo for <a href="https://web.dev/css-trig-functions/" target="_top">https://web.dev/css-trig-functions/</a></p>
</footer>
              
            
!

CSS

              
                @property --angle {
  syntax: '<angle>';
  initial-value: 0deg;
  inherits: true;
}
/* Initial value for browsers that don’t support @property */
:root {
  --angle: 0deg;
}

/* Keyframes that animates the --angle value */
@keyframes adjust-angle {
  to {
    --angle: 360deg;
  }
}

/* Enable animation when checkbox is checked */
:root {
  animation: adjust-angle linear 20s infinite paused;
}
:root:has(#enable_animation:checked) {
  animation-play-state: running;
}

/* The colored dots */
.dot {
  /* Spread the dots evenly over the circle.
     We do this by dividing 360deg by the number of children.
       E.g. 360 degrees / 3 children = 120 degrees between each child element.  
  */
  --offset-per-child: calc(360deg / (var(--nth-siblings) + 1));
  
  /* Each child will that offset into account, based its index.
     E.g. - the 1st out of 3 children gets offset by 0 x 120deg = 0deg
          - the 2nd out of 3 children gets offset by 1 x 120deg = 120deg
          - the 3rd out of 3 children gets offset by 2 x 120deg = 240deg
  */
  --angle-offset: calc(var(--nth-child) * var(--offset-per-child));
  
  /* Make it round */
  display: block;
  width: var(--tracksize);
  aspect-ratio: 1;
  border-radius: 50%;
  
  /* Color it, giving each color a different hue based on the --angle-offset */
  background: hsl(var(--angle-offset) 100% 50%);
  border: 1px solid #333;
  
  /* Center it */
  position: absolute;
  left: calc(50% - (var(--tracksize) / 2));
  top: calc(50% - (var(--tracksize) / 2));
  
  /* Adjust its position based on the --angle, while also taking the --angle-offset into account */
  translate: calc(cos((var(--angle) + var(--angle-offset))) *cos((var(--angle) + var(--angle-offset)))*cos((var(--angle) + var(--angle-offset)))* var(--radius))
           calc(sin((var(--angle) + var(--angle-offset))) *sin((var(--angle) + var(--angle-offset))) *sin((var(--angle) + var(--angle-offset))) * var(--radius) );
  
  /* Other things */
  pointer-events: none;
}


@layer demo {
  @layer visual {
    /* The visualization */
    #visual {
      /* Dimensions of the visualization */
      --radius: 20vmin;
      --tracksize: 5vmin;

      /* Make it a circle, based on the dimensions */
      width: calc(var(--radius) * 2 + var(--tracksize));
      aspect-ratio: 1;
      border-radius: 50%;
      border: var(--tracksize) solid transparent;

      /* Some generic positioning stuff */
      margin: 0 auto;
      position: relative;
    }

    #visual {
      border-color: #e0e0e0;
    }

    /* Inject a dot at the center of the visualization */
    #visual::after {
      content: '';
      --size: calc(var(--tracksize) / 2);

      /* Make it round */
      display: block;
      width: var(--size);
      aspect-ratio: 1;
      border-radius: 50%;

      /* Put it in the center */
      position: absolute;
      left: calc(50% - (var(--size) / 2));
      top: calc(50% - (var(--size) / 2));
      z-index: 2;

      /* Make it black */
      background: #333;
    }
  }
  
  @layer debug {
    /* Draw debug lines for the red dot */
    :root:has(#show_debug:checked) .dot:nth-last-child(1)::before,
    :root:has(#show_debug:checked) .dot:nth-last-child(1)::after {
      /* Inject it */
      content: '';
      display: block;

      /* Color it */
      background: hsl(var(--angle-offset) 100% 50%);

      /* Position it */
      position: absolute;
      left: calc(50%);
      top: calc(50%);
      z-index: -1;

      transform-origin: 0 0;
    }

    :root:has(#show_debug:checked) .dot:nth-last-child(1)::before {
      width: var(--radius);
      height: 2px;

      /* Draw line on horizontal axis*/
      transform: 
        /* Adjust size based on cos() of angle */
        scaleX(cos(calc(var(--angle) + var(--angle-offset))))
        /* Move back so that it goes into the center of the dot */
        translate(-100%, -50%)
        /* Move back so that it appears on X axis instead of on the dot itself */
        translateY(calc(sin((var(--angle) + var(--angle-offset))) * var(--radius)))
      ;
    }

    :root:has(#show_debug:checked) .dot:nth-last-child(1)::after {
      width: 2px;
      height: var(--radius);

      /* Draw line on vertical axis*/
      transform: 
        /* Adjust size based on sin() of angle */
        scaleY(sin(calc((var(--angle) + var(--angle-offset)) * -1)))
        /* Move back so that it goes into the center of the dot */
        translate(-50%, -100%)
      ;
    }
  }
}


@layer demosupport {
  @layer layout {
    label, #controls, form {
      text-align: center;
    }
  } 
}

/* Non-demo styles below */
@layer base {
  @layer reset {
    * {
      box-sizing: border-box;
    }
    body {
      margin: 0;
      padding: 0;
    }
    html, body {
      height: 100%;
    }
  }
  @layer layout {
    html {
      max-width: 84ch;
      padding: 3rem 2rem;
      margin: auto;
    }
    body {
      display: grid;
      place-content: safe center;
      gap: 3rem;
    }

    html {
      --font-sans: system-ui,-apple-system,Segoe UI,Roboto,Ubuntu,Cantarell,Noto Sans,sans-serif,Segoe UI,Roboto,Ubuntu,Cantarell,Noto Sans,sans-serif;
      --font-serif: ui-serif,serif;
      --font-mono: Dank Mono,Operator Mono,Inconsolata,Fira Mono,ui-monospace,SF Mono,Monaco,Droid Sans Mono,Source Code Pro,monospace;
    }
    body {
      font-family: var(--font-sans);
    }
    pre, code {
      font-family: var(--font-mono);
      font-size: 0.8rem;
    }
    input, button {
      font-family: inherit;
    }
    
    a,
    a:visited {
      color: blue;
    }
    
    h2 {
      margin-top: 2em;
    }

    summary {
      cursor: pointer;
    }

    dd + dt {
      margin-top: 0.5em;
    }

    button {
      cursor: pointer;
    }
    
    footer {
      text-align: center;
      font-style: italic;
    }
  }
  
  @layer code {
    pre {
      border: 1px solid #dedede;
      padding: 1em;
      background: #f7f7f7;
      font-family: "Courier 10 Pitch", Courier, monospace;
      overflow-x: auto;
      border-left: 0.4em solid cornflowerblue;
      tab-size: 4;
    }
    
    code:not(pre code), output:not(code:has(output) output) {
      background: #f7f7f7;
      border: 1px solid rgb(0 0 0 / 0.2);
      padding: 0.1rem 0.3rem;
      margin: 0.1rem 0;
      border-radius: 0.2rem;
      display: inline-block;
    }
  }

  @layer support {
    .no-support,
    .has-support {
      margin: 1em 0;
      padding: 1em;
      border: 1px solid #ccc;
    }

    .no-support {
      background-color: #ff00002b;
    }
    .no-support[data-level="warn"] {
      background-color: #ffff002b;
    }
    .has-support {
      background-color: #00ff002b;
    }
    .no-support, [data-show-when-no-support] {
      display: block !important;
    }
    .has-support, [data-show-when-has-support] {
      display: none !important;
    }
    :is(.has-support, .no-support) > :first-child {
      margin-top: 0;
    }
    :is(.has-support, .no-support) > :last-child {
      margin-bottom: 0;
    }
    
    @property --supports-at-property {
      syntax: "*";
      initial-value: ;
      inherits: true;
    }
    .no-support[data-support="at-property"], [data-no-support="at-property"] {
      --value-when-supported: var(--supports-at-property) none;
      --value-when-not-supported: block;
      display: var(--value-when-supported, var(--value-when-not-supported)) !important;
    }
    .has-support[data-support="at-property"], [data-has-support="at-property"] {
      --value-when-supported: var(--supports-at-property) block;
      --value-when-not-supported: none;
      display: var(--value-when-supported, var(--value-when-not-supported)) !important;
    }

    @supports (transform: scaleX(cos(360deg))) {
      .no-support[data-support="css-trig-fns"] {
        display: none !important;
      }
      .has-support[data-support="css-trig-fns"], [data-show-when-has-support="css-trig-fns"] {
        display: block !important;
      }
    }
  }
  
  @layer nth-child {
    [data-countchildren] > :nth-child(1) {
      --nth-child: 1;
    }
    [data-countchildren] > :nth-child(2) {
      --nth-child: 2;
    }
    [data-countchildren] > :nth-child(3) {
      --nth-child: 3;
    }
    [data-countchildren] > :nth-child(4) {
      --nth-child: 4;
    }
    [data-countchildren] > :nth-child(5) {
      --nth-child: 5;
    }
    [data-countchildren] > :nth-child(6) {
      --nth-child: 6;
    }
    [data-countchildren] > :nth-child(7) {
      --nth-child: 7;
    }
    [data-countchildren] > :nth-child(8) {
      --nth-child: 8;
    }
    [data-countchildren] > :nth-child(9) {
      --nth-child: 9;
    }
    [data-countchildren] > :nth-child(10) {
      --nth-child: 10;
    }

    [data-countchildren]:has(> :nth-child(1):last-child) > * {
      --nth-siblings: 0;
    }
    [data-countchildren]:has(> :nth-child(2):last-child) > * {
      --nth-siblings: 1;
    }
    [data-countchildren]:has(> :nth-child(3):last-child) > * {
      --nth-siblings: 2;
    }
    [data-countchildren]:has(> :nth-child(4):last-child) > * {
      --nth-siblings: 3;
    }
    [data-countchildren]:has(> :nth-child(5):last-child) > * {
      --nth-siblings: 4;
    }
    [data-countchildren]:has(> :nth-child(6):last-child) > * {
      --nth-siblings: 5;
    }
    [data-countchildren]:has(> :nth-child(7):last-child) > * {
      --nth-siblings: 6;
    }
    [data-countchildren]:has(> :nth-child(8):last-child) > * {
      --nth-siblings: 7;
    }
    [data-countchildren]:has(> :nth-child(9):last-child) > * {
      --nth-siblings: 8;
    }
    [data-countchildren]:has(> :nth-child(10):last-child) > * {
      --nth-siblings: 9;
    }
  }
}

              
            
!

JS

              
                
              
            
!
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