style.css

:root {
    --line-color: #000000;
    --font-color: rgb(0, 0, 0);
    --font-course-text-color: #ffffff;
    --bg-color: #fff;
    --svg-bg-color: #ffffff;
    --grid-color: silver;
    --github-image: 'images/github-white.png';
}

[data-theme="dark"] {
    --line-color: #000000;
    --font-color: #e1e1ff;
    --font-course-text-color: #ffffff;
    --bg-color: #161625;
    --svg-bg-color: #161625;
    --grid-color: #47475c;
    --github-image: 'images/github.png';
}

body {
    background: var(--bg-color);
}
svg {
    font: 13px sans-serif;
    background: var(--svg-bg-color);
    display:block;
    margin:0 auto;
}
text {
    font: 12px sans-serif;
    fill: var(--font-color);
    color: var(--font-color);
}
.course-text {
    font: 11px sans-serif;
    fill: var(--font-course-text-color);
    color: var(--font-course-text-color);
}
.chart rect {
    stroke: white;
}
rect.section {
    cursor: ns-resize;
}
.line {
    fill:none;
    stroke: var(--line-color);
    stroke-width:1.5px;
}
.axis path, .axis line {
    fill: none;
    stroke: var(--grid-color);
    shape-rendering: crispEdges;
}
.axis path {
    display: none;
}
.grid {
    fill: none;
    stroke-width: 0.5px;
    stroke: var(--line-color);
    opacity: 0.2;
}
#wrap {
    width:910px;
    margin:0 auto;
}


a {
    color: var(--font-color);
    font-family: helvetica;
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}
a:active {
    color: var(--font-color);
}
a:visited {
    color: var(--font-color);
}


/* The switch - the box around the slider */
.theme-switch {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 34px;
}
/* Hide default HTML checkbox */
.theme-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}
/* The slider */
.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #ccc;
    -webkit-transition: .4s;
    transition: .4s;
}
.slider:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    -webkit-transition: .4s;
    transition: .4s;
}
input:checked + .slider {
    background-color: #2196F3;
}
input:focus + .slider {
    box-shadow: 0 0 1px #2196F3;
}
input:checked + .slider:before {
    -webkit-transform: translateX(26px);
    -ms-transform: translateX(26px);
    transform: translateX(26px);
}
/* Rounded sliders */
.slider.round {
    border-radius: 34px;
}
.slider.round:before {
    border-radius: 50%;
}