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HTML

            
              <form method="get">
  <input type="checkbox" name="mode" id="mode" value="night" onclick="modecheck()">
  <label for="mode">
  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 333.3 169">
	<path id="Peanut" d="M115,17.3c13.9,5.4,30.7,9.8,49.4,9.8 c18.8,0,36.1-3.7,49.7-10c9-4,19-6.3,29.5-6.3c40,0,72.4,32.4,72.4,72.4s-32.4,72.4-72.4,72.4c-10.7,0-20.8-2.3-30-6.5h-0.1 c-13.6-6.1-30.7-9.8-49.4-9.8c-18.4,0-35.4,3.6-48.8,9.6l0,0c-9.1,4.1-19.2,6.4-29.9,6.4C45.5,155.4,13,123,13,83 s32.4-72.4,72.4-72.4C98.7,10.6,105.3,13.5,115,17.3z" />
</svg>
	<span class="initial"></span>
	<span class="follower"></span>
  </label>
</form>
<section>
  <h1>From The Earth To The Moon</h1>
  <h2><img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/4273/jules-verne-autograph.svg" alt="Jules Verne" class="switch"></h2>
  <h3><span>Chapter I</span>The Gun Club</h3>
<p>During the War of the Rebellion, a new and influential club was established in the city of Baltimore in the State of Maryland. It is well known with what energy the taste for military matters became developed among that nation of ship-owners, shopkeepers, and mechanics. Simple tradesmen jumped their counters to become extemporized captains, colonels, and generals, without having ever passed the School of Instruction at West Point; nevertheless; they quickly rivaled their compeers of the old continent, and, like them, carried off victories by dint of lavish expenditure in ammunition, money, and men.</p>

<p><img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/4273/earth-moon-sun-system.png" id="diagram" alt="Diagram of Earth-Moon-Sun system">But the point in which the Americans singularly distanced the Europeans was in the science of gunnery. Not, indeed, that their weapons retained a higher degree of perfection than theirs, but that they exhibited unheard-of dimensions, and consequently attained hitherto unheard-of ranges. In point of grazing, plunging, oblique, or enfilading, or point-blank firing, the English, French, and Prussians have nothing to learn; but their cannon, howitzers, and mortars are mere pocket-pistols compared with the formidable engines of the American artillery.</p>

<p>This fact need surprise no one. The Yankees, the first mechanicians in the world, are engineers-- just as the Italians are musicians and the Germans metaphysicians-- by right of birth. Nothing is more natural, therefore, than to perceive them applying their audacious ingenuity to the science.</p>

</section>
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CSS

            
              @font-face {
    font-family: 'IM Fell French Canon Pro';
    src: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/4273/im-fell-french-canon-pro.woff2') format('woff2'),
         url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/4273/im-fell-french-canon-pro.woff') format('woff');
    font-weight: normal;
    font-style: normal;
}
@keyframes sideslide {
		0% { 
      transform: translateX(0%) scale(1); 
  }
		50% { 
      transform: translateX(67%) scale(.75); 
  }
		100% { 
      transform: translateX(134%) scale(1); 
      background: white;
  }		
	}

body { 
  font-family: IM Fell French Canon Pro, script;
  margin: 3rem;
}

label[for="mode"] { 
    display: block;
		padding-top: 10%;
		width: 10%;
    min-width: 100px;
		position: relative;
	}
label[for="mode"]:hover {
  cursor: pointer;
}
	label[for="mode"] svg { 
		position: absolute; 
		top: 0;
		fill: #b7eaff;
		transition: .8s;
	}
  label[for="mode"] span {
		position: absolute;
		display: block;
		width: 35%;
		height: 35%;
		background: yellow;
		top: 7%;
		left: 8%;
		border-radius: 50%;
	}
#mode { display: none; }
#mode:checked + label span {
		animation: sideslide .8s forwards;
	}
#mode:checked + label span.follower {
		animation-delay: .07s;
	}
#mode:checked + label svg {
		fill: #191621;
    stroke-width: 1px;
    stroke: white;
	}
section { 
  max-width: 40rem;
  line-height: 1.4;
  margin: 0 auto;
  h1 {
    font-size: 3rem;
    margin-top: -3rem;
  }
  h2 {
    text-align: center;
    margin: 0;
  img {
    width: 50%;
    min-width: 200px;
  }
  }
  h3 { 
    font-size: 2.3rem;
    text-align: center;
    span {
      display: block;
      &:after {
        content: ":";
      }
    }
  }
  p {
      font-size: 1.4rem;
  }
  #diagram {
    float: right;
    margin-left: 3rem;
    width: 17.8rem;
    @media all and (max-width: 600px) {
      float: none;
      display: block;
      width: 75%;
      margin: 0 auto;
    }
  }
}
body { 
  transition: 2s background, color; }
.night {
  body { 
    background: #000; 
    color: #fff;
  }
  img.switch { 
    filter: invert(100%);
  }
  
}
@media (light-level: dim) {
  // from CSS Luminosity Media Queries: https://drafts.csswg.org/mediaqueries4/#luminosity
  // currently only supported in FF
  body { 
    background: #000; 
    color: #fff;
  }
  img.switch { 
    filter: invert(100%);
  }
}
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JS

            
              var mode = document.getElementById("mode");
var lux;
window.addEventListener('devicelight', function(e) {
  lux = e.value;
  // AmbientLight API - not well-supported right now
})
var currentTime = new Date().getHours();

function modecheck() {
  if (mode.checked) {
 document.documentElement.classList.add('night');
  } else {
 document.documentElement.classList.remove('night'); 
  }
}

function timeCheck() {
  if (currentTime > 18 || currentTime < 6 || lux < 50) {
      mode.checked = true;
  }
}

function callEveryHour() {
    setInterval(timeCheck(), 1000 * 60 * 60);
}
timeCheck();
modecheck();
!
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