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HTML 

              
                <main id="app" class="dark">
    
    <header>
        <h1>A Gooey button</h1>
        <p>Hover to experience! (single element)</p>
    </header>
    
    <div>
    
        <button type="button">
            Gooey Button
        </button>
        
    </div>
    
    <p>Inspired by <em>(and svg filter copied from)</em> <a target="_blank" href="https://codepen.io/thebabydino/pen/NWVdKaG">Ana's codepen</a>, go give her a ❤️ !</p>

</main>


<svg width="0" height="0" style="position: absolute;">
  <filter id="goo" x="-50%" y="-50%" width="200%" height="200%">
    <feComponentTransfer>
      <feFuncA type="discrete" tableValues="0 1"></feFuncA>
    </feComponentTransfer>
    <feGaussianBlur stdDeviation="5"></feGaussianBlur>
    <feComponentTransfer>
      <feFuncA type="table" tableValues="-5 11"></feFuncA>
    </feComponentTransfer>
  </filter>
</svg>

<!-- 













    social icons
-->
<a class="social-icon codepen" href="https://codepen.io/simeydotme" title="view my codepens">
    Made by Simey
</a>

<a class="social-icon twitter" href="https://twitter.com/simeydotme">
    <svg viewBox="0 0 24 24">
        <path stroke="none" d="M0 0h24v24H0z" fill="none"></path>
        <path d="M22 4.01c-1 .49 -1.98 .689 -3 .99c-1.121 -1.265 -2.783 -1.335 -4.38 -.737s-2.643 2.06 -2.62 3.737v1c-3.245 .083 -6.135 -1.395 -8 -4c0 0 -4.182 7.433 4 11c-1.872 1.247 -3.739 2.088 -6 2c3.308 1.803 6.913 2.423 10.034 1.517c3.58 -1.04 6.522 -3.723 7.651 -7.742a13.84 13.84 0 0 0 .497 -3.753c-.002 -.249 1.51 -2.772 1.818 -4.013z"></path>
    </svg>
</a>
<a class="social-icon github" href="https://github.com/simeydotme">
    <svg viewBox="0 0 24 24">
        <path stroke="none" d="M0 0h24v24H0z" fill="none"></path>
        <path d="M9 19c-4.3 1.4 -4.3 -2.5 -6 -3m12 5v-3.5c0 -1 .1 -1.4 -.5 -2c2.8 -.3 5.5 -1.4 5.5 -6a4.6 4.6 0 0 0 -1.3 -3.2a4.2 4.2 0 0 0 -.1 -3.2s-1.1 -.3 -3.5 1.3a12.3 12.3 0 0 0 -6.2 0c-2.4 -1.6 -3.5 -1.3 -3.5 -1.3a4.2 4.2 0 0 0 -.1 3.2a4.6 4.6 0 0 0 -1.3 3.2c0 4.6 2.7 5.7 5.5 6c-.6 .6 -.6 1.2 -.5 2v3.5"></path>
    </svg>
</a>
!

CSS 

              
                @property --a {
    syntax: "<percentage>";
    initial-value: 0%;
    inherits: true;
}

.dark button {
    --a: 0%;
    --hue: 170deg;
    --x: 50;
    --y: 50;
    --button: hsl(var(--hue), 66%, 66%);
    --edge: 20px;
    --size: 2em;
    
    background: transparent;
    color: hsla(var(--hue), 80%, 30%, 0.7);
    font-size: 1.8em;
    position: relative;
    padding: calc(var(--size)) calc(var(--size)*1.5);
    animation: color 20s linear infinite both;
    transition: 
        --a .5s ease-in-out, 
        scale var(--spring-duration) var(--spring-easing);
    scale: 0.92;
    isolation: isolate;
    &:hover {
        --a: 100%;
        transition-duration: .5s, 1s;
        box-shadow: none;
        opacity: 1;
        scale: 1;
    }
}

button:before {
    content: "";
    position: absolute;
    inset: 0em;
    /** here's the magic. A blur and a svg filter */
    filter: blur(12px) url(#goo) drop-shadow(0 .25em .5em hsla(0deg, 0%, 0%, 0.8)); 
    /** followed by a radial-gradient which causes the
    gooey effect to follow mouse-position */
    background-image:
        linear-gradient(0deg,var(--button),var(--button)),
        radial-gradient(
            40% 70% at calc(var(--x) * 1%) calc(var(--y) * 1%),
            hsla(var(--hue), 77%, 77%, var(--a)) 0%,
            transparent 90%
        );
    /** and finally a background-clip so the radial-gradient
    is larger than the linear-gradient */
    background-clip: content-box, border-box;
    padding: 24px;
    z-index: -1;
    border: inherit;
    animation: color 20s linear infinite both;
}
















@property --hue {
    syntax: "<angle>";
    initial-value: 170deg;
    inherits: false;
}

@keyframes color {
    from {
        --hue: 170deg;
    }
    to {
        --hue: 530deg;
    }
}

body, html {
    height: 100%;
}

main {
    display: grid;
    place-items: center;
    color: var(--light);
    text-align: center;
}

:root {
    --spring-easing: linear(
    0, 0.002, 0.01 0.9%, 0.038 1.8%, 0.156, 0.312 5.8%, 0.789 11.1%, 1.015 14.2%,
    1.096, 1.157, 1.199, 1.224 20.3%, 1.231, 1.231, 1.226, 1.214 24.6%,
    1.176 26.9%, 1.057 32.6%, 1.007 35.5%, 0.984, 0.968, 0.956, 0.949 42%,
    0.946 44.1%, 0.95 46.5%, 0.998 57.2%, 1.007, 1.011 63.3%, 1.012 68.3%,
    0.998 84%, 1
  );
    --spring-duration: 1.66s;
}
!

JS 

              
                /** 
    very simply js to capture mouse position 
    and set variables to the % location. Everything else is css/svg.
**/
function moveBg(e) {
    const rect = e.target.getBoundingClientRect();
    e.target.style.setProperty('--x', (e.clientX - rect.x) / rect.width * 100);
    e.target.style.setProperty('--y', (e.clientY - rect.y) / rect.height * 100);
}
document.querySelector("button").addEventListener('pointermove', moveBg);


























/** just some JS for the intro animation, nothing here is needed
for the gooey interaction. **/
let x;
function intro() {
    let i = 4; 
    let $b = document.querySelector("button");
    $b.style.setProperty( "--a", '100%' );
    x = setInterval(() => {
        $b.style.setProperty( 
            "--x", ((Math.cos(i) + 2) / 3.6) * 100
        );
        $b.style.setProperty( 
            "--y", ((Math.sin(i) + 2) / 3.6) * 100
        );
        i+= 0.03;
        if( i > 11.5 ) {
            clearInterval(x);
            $b.style.setProperty( "--a", '' );
        }
    },16);
}
intro();
document.querySelector("button").addEventListener('pointerover', (e) => {
    clearInterval(x);
    e.target.style.setProperty( "--a", '' );
});
!
999px

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