:root {
    --navy: #192a40;
    --navy-dark: #0f172a;
    --orange: #e85130;
    --orange-dark: #b4530f;
    --slate: #475569;
    --slate-light: #94a3b8;
    --bg: #f1f5f9;
    --card: #ffffff;
    --border: #e2e8f0;
    --green: #65a30d;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    background: var(--bg);
    color: var(--navy);
    line-height: 1.6;
}

header {
    background: var(--navy);
    color: #fff;
    position: sticky;
    top: 0;
    z-index: 10;
    box-shadow: 0 2px 8px rgba(15, 23, 42, .3);
}

.header-inner {
    max-width: 1000px;
    margin: 0 auto;
    padding: .75rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
}

.logo { font-size: 1.125rem; font-weight: 600; letter-spacing: -.02em; display: flex; align-items: center; gap: .5rem; }
.logo img { height: 1.5rem; width: 1.5rem; }
.logo em { color: var(--orange); font-style: normal; }
.logo small { color: var(--slate-light); font-weight: 400; margin-left: .6rem; font-size: .85rem; }

.lang-switch a {
    color: #cbd5e1;
    text-decoration: none;
    border: 1px solid var(--slate);
    border-radius: 6px;
    padding: .25rem .7rem;
    font-size: .85rem;
}
.lang-switch a:hover { color: #fff; border-color: var(--slate-light); }

.header-actions { display: flex; align-items: center; gap: .75rem; }

.print-btn {
    color: #cbd5e1;
    background: transparent;
    border: 1px solid var(--slate);
    border-radius: 6px;
    padding: .25rem .7rem;
    font-size: .85rem;
    font-family: inherit;
    cursor: pointer;
}
.print-btn:hover { color: #fff; border-color: var(--slate-light); }

main {
    max-width: 1000px;
    margin: 0 auto;
    padding: 2rem 1.5rem 4rem;
}

nav.toc {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.25rem 1.5rem;
    margin-bottom: 2.5rem;
}
nav.toc strong { display: block; margin-bottom: .5rem; }
nav.toc ol { margin: 0; padding-left: 1.4rem; columns: 2; column-gap: 3rem; }
nav.toc li { margin: .2rem 0; break-inside: avoid; }
nav.toc a { color: var(--orange-dark); text-decoration: none; }
nav.toc a:hover { text-decoration: underline; }

section { margin-bottom: 3.5rem; }

h1 { font-size: 2rem; letter-spacing: -.02em; margin: 0 0 .3rem; }
.subtitle { color: var(--slate); margin: 0 0 2rem; }

h2 {
    font-size: 1.45rem;
    border-bottom: 3px solid var(--orange);
    display: inline-block;
    padding-bottom: .15rem;
    margin: 0 0 1rem;
    scroll-margin-top: 5rem;
}

h3 { font-size: 1.05rem; margin: 1.75rem 0 .5rem; }

p, ul, ol { margin: .6rem 0; }
li { margin: .25rem 0; }

figure {
    margin: 1.5rem 0;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1rem;
    box-shadow: 0 1px 3px rgba(15, 23, 42, .06);
}
figure img {
    width: 100%;
    height: auto;
    border-radius: 8px;
    border: 1px solid var(--border);
    display: block;
}
figcaption {
    color: var(--slate);
    font-size: .875rem;
    padding-top: .6rem;
    text-align: center;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 12px;
    overflow: hidden;
    font-size: .925rem;
    margin: 1rem 0;
}
th, td { padding: .55rem .8rem; text-align: left; border-bottom: 1px solid var(--border); vertical-align: top; }
th { background: var(--navy); color: #fff; font-weight: 600; }
tr:last-child td { border-bottom: none; }
td.num { text-align: right; font-variant-numeric: tabular-nums; }

.badge {
    display: inline-block;
    background: #ffedd5;
    color: #9a3412;
    border-radius: 999px;
    padding: .05rem .6rem;
    font-size: .8rem;
    font-weight: 600;
    white-space: nowrap;
}
.badge.green { background: #ecfccb; color: #3f6212; }

.tip, .note {
    border-left: 4px solid var(--orange);
    background: #fff7ed;
    border-radius: 0 10px 10px 0;
    padding: .75rem 1rem;
    margin: 1rem 0;
    font-size: .925rem;
}
.note { border-left-color: var(--navy); background: #f8fafc; }

.formula {
    background: var(--navy-dark);
    color: #e2e8f0;
    border-radius: 10px;
    padding: 1rem 1.25rem;
    font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
    font-size: .9rem;
    overflow-x: auto;
    margin: 1rem 0;
}
.formula b { color: var(--orange); }

.steps { counter-reset: step; list-style: none; padding-left: 0; }
.steps > li {
    counter-increment: step;
    position: relative;
    padding-left: 2.5rem;
    margin: .75rem 0;
}
.steps > li::before {
    content: counter(step);
    position: absolute;
    left: 0;
    top: .1rem;
    width: 1.7rem;
    height: 1.7rem;
    border-radius: 50%;
    background: var(--orange);
    color: #fff;
    font-weight: 700;
    font-size: .9rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

footer {
    text-align: center;
    color: var(--slate-light);
    font-size: .85rem;
    padding: 2rem 0 3rem;
}

@media (max-width: 700px) {
    nav.toc ol { columns: 1; }
}

@media print {
    body { background: #fff; }
    header { position: static; box-shadow: none; }
    .header-actions { display: none; }
    nav.toc { border: 1px solid var(--border); break-inside: avoid; }
    section { margin-bottom: 2rem; }
    h2 { break-after: avoid; }
    figure, table, .tip, .note, .formula, .steps > li { break-inside: avoid; }
    a { color: inherit; text-decoration: underline; }

    * {
        -webkit-print-color-adjust: exact;
        print-color-adjust: exact;
    }
}