batterieapp_style.css

 * {
	border: 0;
	margin: 0;
	padding: 0;
	box-sizing: border-box;
}

:root {
	--color-white: rgb(254, 254, 254);
	--color-white-light: rgba(254, 254, 254, .6);
	--color-green: #509000;
	--color-blue: #1c69d4;
	--color-blue-light: #C7EEFF;
	--color-red: #F90000;
	--color-orange: #DC9012;
	--color-purple: #f0f;
	--color-cyan: #0ff;
	--color-main-border: #222a32;
	--color-page-gradient-from: #485563;
	--color-page-gradient-to: #29323c;
}

@font-face {
	font-family: 'Advent Pro';
	font-style: normal;
	font-weight: 100;
	src: local('Advent Pro Thin'), local('AdventPro-Thin'), url('./fonts/advent-pro-100-reduced.woff2?2017-01-21-v3') format('woff2');
}

html {
	height: 100%;

	background: linear-gradient( to bottom right, var(--color-page-gradient-from), var(--color-page-gradient-to) );

	color: var(--color-white);
	font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
	text-transform: uppercase;
	text-align: center;

	-webkit-font-smoothing: antialiased;
}
h2 {
	font-size: 22px;
	font-weight: 200;
	line-height: 24px;
	letter-spacing: 1px;
}
h4 {
	color: var(--color-white-light);
	font-size: 14px;
	font-weight: 200;
	line-height: 16px;
	letter-spacing: 1px;
}
units {
	font-size: 14px;
	font-weight: 200;
	line-height: 16px;
	letter-spacing: 1px;
}
footerdatetext {
	font-size: 9px;
	font-weight: 200;
	line-height: 16px;
	letter-spacing: 1px;
}			
section {
	margin-bottom: 20px;

	flex-basis: 50%;
	max-width: 50%;
}

header {
	top: 0;
	width: 100%;
	padding: 45px 0 4px;
	position: absolute;
}
footer {
	width: 100%;
	height: 36%;
	bottom: 0;
	position: absolute;

	display: flex;
	flex-flow: row wrap;
	align-items: center;
	justify-content: center;
}

header,
footer {
	opacity: 1;

	transition: opacity .25s;
}
header:empty,
footer:empty {
	opacity: 0;
}

main {
	top: 35%;
	left: 50%;
	width: 200px;
	height: 200px;
	position: absolute;

	border: 12px solid var(--color-main-border);
	border-radius: 100%;
	overflow: hidden;

	transform: translate(-50%, -50%);

	box-shadow: 0 0 0 transparent;
	transition: all 1.6s cubic-bezier(0.165, 0.84, 0.44, 1);
}

.loading main {
	display: flex;
	align-items: center;
	justify-content: center;

	animation: pulse 1.7s infinite;
}
.loading main::after {
	display: block;
	content: 'Updating';

	color: var(--color-white);
	font-size: 22px;
	font-weight: 200;
	line-height: 24px;
	letter-spacing: 1px;
}

.percent {
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
	position: absolute;

	z-index: 3;

	display: flex;
	align-items: center;
	justify-content: center;
}
.percent::before {
	content: attr(data-percent);
	display: block;

	font-family: 'Advent Pro';
	font-size: 80px;
	line-height: 80px;
	font-weight: 100;

	text-rendering: optimizeLegibility;
}
.percent::after {
	top: 58px;
	right: 20px;
	position: absolute;

	content: '%';
	display: block;

	font-size: 26px;
	line-height: 26px;
	font-weight: 100;

	opacity: .6;
}

.water {
	bottom: 0;
	left: 0;
	width: 100%;
	position: absolute;

	z-index: 2;

	background: var(--color-green);
}

.wave {
	width: 200%;
	bottom: 100%;
	display: none;
	position: absolute;
}
.wave-back {
	right: 0;

	fill: var(--color-blue-light);

	animation: wave-back 1.4s infinite linear;
}
.wave-front {
	left: 0;
	margin-bottom: -1px;

	fill: var(--color-blue);

	animation: wave-front .7s infinite linear;
}

@keyframes wave-front {
	100% {
		transform: translate(-50%, 0);
	}
}
@keyframes wave-back {
	100% {
		transform: translate(50%, 0);
	}
}
@keyframes pulse {
	50% {
		box-shadow: -5px 0 20px var(--color-purple), 5px 0 20px var(--color-cyan);
	}
}

[data-percent^="0"] + .water,
[data-percent^="1"] + .water,
[data-percent^="2"] + .water {
	background: var(--color-red);
}
[data-percent^="3"] + .water,
[data-percent^="4"] + .water {
	background: var(--color-orange);
}
[data-percent="100"] + .water {
	background: var(--color-green);
}

[data-charging="1"].water {
	background: var(--color-blue);
}
[data-charging="1"] .wave {
	display: block;
}