* {
    box-sizing: border-box
}

:root {
    --bg: #fff;
    --fg: #1c1b22;
    --mut: #6b6a75;
    --ac: #4f46e5;
    --card: #f5f5fa;
    --bd: #e4e4ee;
    --code: #14141f
}

@media(prefers-color-scheme:dark) {
    :root {
        --bg: #121218;
        --fg: #ececf3;
        --mut: #9a99a8;
        --ac: #8b85ff;
        --card: #1b1b24;
        --bd: #2c2c3a
    }
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--fg);
    font: 17px/1.7 system-ui, sans-serif
}

a {
    color: var(--ac)
}

.wrap {
    max-width: 820px;
    margin: 0 auto;
    padding: 0 20px
}

header.top {
    border-bottom: 1px solid var(--bd);
    padding: 14px 0
}

header.top .wrap {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    flex-wrap: wrap
}

header.top a {
    text-decoration: none;
    font-weight: 600
}

h1 {
    font-size: clamp(1.8rem, 5vw, 2.6rem);
    line-height: 1.2;
    margin: 40px 0 8px
}

h2 {
    margin: 0 0 8px;
    font-size: 1.35rem
}

.sub {
    color: var(--mut)
}

.grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 14px;
    margin: 28px 0
}

.card {
    display: block;
    background: var(--card);
    border: 1px solid var(--bd);
    border-radius: 12px;
    padding: 16px;
    text-decoration: none;
    color: inherit;
    transition: transform .2s
}

.card:hover {
    transform: translateY(-3px)
}

.card b {
    color: var(--ac)
}

.card small {
    color: var(--mut);
    display: block
}

.soon {
    opacity: .6
}

.toc {
    background: var(--card);
    border-radius: 12px;
    padding: 12px 45px;
    margin: 20px 0
}

.lesson {
    border-top: 1px solid var(--bd);
    padding: 28px 0
}

.n {
    color: var(--ac);
    font-weight: 700
}

pre {
    background: var(--code);
    color: #e8e8f2;
    padding: 14px;
    border-radius: 10px;
    overflow-x: auto;
    font-size: 14px;
    line-height: 1.55
}

code {
    background: var(--card);
    padding: 1px 6px;
    border-radius: 5px;
    font-size: .9em
}

pre code {
    background: none;
    padding: 0
}

.nav {
    display: flex;
    justify-content: space-between;
    gap: 10px;
    padding: 30px 0 50px;
    border-top: 1px solid var(--bd)
}

footer {
    color: var(--mut);
    text-align: center;
    padding: 30px 0
}