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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <p>Cool Underlines With CSS Gradients</p>

<h1><span class="rainbow">Standard Rainbow</span></h1>
<h1><span class="rainbow-energetic">Energetic Rainbow</span></h1>

<h1><span class="tapered">This One is Tapered!</span></h1>
<h1><span class="tapered2">This One Grows!</span></h1>

<h1><span class="double">Double Underline</span></h1>
<h1><span class="triple">Rare Triple Underline</span></h1>

<h1><span class="graph-paper">Graph Paper</span></h1>
<h1><span class="weave">Blue Weave</span></h1>

<h1><span class="green">Shades of Green</span></h1>
<h1><span class="purple">Shades of Purple</span></h1>

<h1><span class="purple-orange">Purple and Orange</span></h1>
<h1><span class="yellow-orange">Yellow to Orange</span></h1>

<footer>
  Made with <a href="http://www.gradientmagic.com" target="_blank">Gradient Magic</a>, inspired by <a href="https://codepen.io/chriscoyier/pen/qBBMYYb" target="_blank">this pen</a>.
</footer>
!

CSS 

              
                body {
  font-weight: 900;
  font-size: 36px;
  font-family: system-ui, -apple-system, sans-serif;
  letter-spacing: -1px;
  padding: 0 0 2rem 2rem;
}

p {
  margin-bottom: 4rem;
}

h1 {
  margin-bottom: 3.5rem;
  span {
   background-size:  100% 15%;
   background-repeat: repeat-x;
   background-position: left 0% bottom 10%;
  }
}


.rainbow {
    background-image: linear-gradient(90deg, hsl(284,91%,69%) 0%, hsl(284,91%,69%) 12.5%,hsl(329,91%,69%) 12.5%, hsl(329,91%,69%) 25%,hsl(14,91%,69%) 25%, hsl(14,91%,69%) 37.5%,hsl(59,91%,69%) 37.5%, hsl(59,91%,69%) 50%,hsl(104,91%,69%) 50%, hsl(104,91%,69%) 62.5%,hsl(149,91%,69%) 62.5%, hsl(149,91%,69%) 75%,hsl(194,91%,69%) 75%, hsl(194,91%,69%) 87.5%,hsl(239,91%,69%) 87.5%, hsl(239,91%,69%) 100%);
}

.rainbow-energetic {
  background-image: repeating-linear-gradient(135deg, hsl(46,80%,67%) 0px, hsl(46,80%,67%) 14px,hsl(91,80%,67%) 14px, hsl(91,80%,67%) 28px,hsl(136,80%,67%) 28px, hsl(136,80%,67%) 42px,hsl(181,80%,67%) 42px, hsl(181,80%,67%) 56px,hsl(226,80%,67%) 56px, hsl(226,80%,67%) 70px,hsl(271,80%,67%) 70px, hsl(271,80%,67%) 84px,hsl(316,80%,67%) 84px, hsl(316,80%,67%) 98px,hsl(1,80%,67%) 98px, hsl(1,80%,67%) 112px);
}

.tapered {
  background-image: linear-gradient(179deg,rgb(254, 97, 158) 0%, rgb(254, 97, 158) 50%,transparent 54%, transparent 100%);
}

.tapered2 {
  background-image: linear-gradient(181deg, #ffa620 0%, #fba11a 50%, transparent 54%, transparent 100%);
}

.double {
  background-image: repeating-linear-gradient(0deg, rgb(246, 96, 94) 0px, rgb(246, 96, 94) 4px,transparent 4px, transparent 8px,rgb(249, 139, 40) 8px, rgb(249, 139, 40) 12px,transparent 12px, transparent 16px),linear-gradient(90deg, #FFF,#FFF);
}

.triple {
  background-image: repeating-linear-gradient(0deg, rgb(42, 166, 224) 0px, rgb(42, 166, 224) 4px,transparent 4px, transparent 8px,rgb(48, 200, 159) 8px, rgb(48, 200, 159) 12px,transparent 12px, transparent 16px,rgb(53, 234, 94) 16px, rgb(53, 234, 94) 20px,transparent 20px, transparent 24px),linear-gradient(90deg, #FFF,#FFF);
  background-size: 100% 24%;
  background-position: 100% 98%;
}


.graph-paper {
  background-image: repeating-linear-gradient(0deg, hsl(144,66%,90%) 0px, hsl(144,66%,90%) 2px,transparent 2px, transparent 7px),repeating-linear-gradient(90deg, hsl(144,66%,90%) 0px, hsl(144,66%,90%) 2px,transparent 2px, transparent 7px),linear-gradient(90deg, hsl(218,79%,50%),hsl(218,79%,50%));
}

.weave {
  background-image: repeating-linear-gradient(135deg, rgb(99, 171, 222) 0px, rgb(99, 171, 222) 7px,transparent 7px, transparent 14px),repeating-linear-gradient(45deg, rgb(38, 95, 221) 0px, rgb(38, 95, 221) 7px,transparent 7px, transparent 14px),repeating-linear-gradient(135deg, #FFF 0px, #FFF 7px,#FFF 7px, #FFF 14px);
}

.green {
background-image: repeating-linear-gradient(90deg, rgb(79, 191, 86) 0px, rgb(79, 191, 86) 16px,rgb(59, 180, 83) 16px, rgb(59, 180, 83) 32px,rgb(30, 162, 80) 32px, rgb(30, 162, 80) 48px,rgb(40, 168, 81) 48px, rgb(40, 168, 81) 64px,rgb(88, 197, 87) 64px, rgb(88, 197, 87) 80px,rgb(98, 203, 88) 80px, rgb(98, 203, 88) 96px,rgb(49, 174, 82) 96px, rgb(49, 174, 82) 112px,rgb(69, 185, 85) 112px, rgb(69, 185, 85) 128px)
}

.purple {
  background-image: repeating-linear-gradient(135deg, rgb(180, 96, 226) 0px, rgb(180, 96, 226) 45px,rgb(196, 124, 232) 45px, rgb(196, 124, 232) 76px,rgb(165, 69, 221) 76px, rgb(165, 69, 221) 114px,rgb(211, 151, 237) 114px, rgb(211, 151, 237) 127px,rgb(242, 206, 248) 127px, rgb(242, 206, 248) 139px,rgb(227, 179, 243) 139px, rgb(227, 179, 243) 170px);
}

.purple-orange {
  background-image: linear-gradient(90deg, rgb(246, 137, 24) 0%, rgb(246, 137, 24) 31%,rgb(174, 62, 159) 31%, rgb(174, 62, 159) 42%,rgb(210, 100, 92) 42%, rgb(210, 100, 92) 49%,rgb(138, 25, 227) 49%, rgb(138, 25, 227) 100%);
}

.yellow-orange {
  background-image: linear-gradient(90deg, rgb(218, 230, 1) 0%, rgb(218, 230, 1) 7%,rgb(226, 203, 7) 7%, rgb(226, 203, 7) 14%,rgb(234, 176, 13) 14%, rgb(234, 176, 13) 21%,rgb(242, 148, 18) 21%, rgb(242, 148, 18) 28%,rgb(250, 121, 24) 28%, rgb(250, 121, 24) 100%);
  background-size: 100% 18%;
}

footer {
  font-size: 24px;
  font-weight: 500;
  a {
    color: #007bff;
    text-decoration: none;
  }
}
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