* {
    box-sizing: border-box;
}

:root {
    --sk-primary: #1976d2;
    --sk-primary-dark: #0d47a1;
    --sk-primary-soft: #e3f2fd;
    --sk-primary-border: #bbdefb;
    --sk-accent: #00bfff;
    --sk-text: #1f2937;
    --sk-muted: #5f6f82;
    --sk-surface: #ffffff;
    --sk-page: #f5f8fc;
    --sk-border: #d7e6f7;
}
body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background: var(--sk-page);
    color: var(--sk-text);
    line-height: 1.6;
}

.container-fluid {
    padding: 0;
}

.sidebar {
    background: var(--sk-surface);
    min-height: 100vh;
    position: fixed;
    top: 0;
    left: 0;
    padding: 22px 16px;
    border-right: 1px solid var(--sk-primary-border);
    box-shadow: 8px 0 24px rgba(31, 41, 55, 0.06);
    z-index: 10;
}

.sidebar-brand {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 6px 4px 20px;
    margin-bottom: 12px;
    border-bottom: 1px solid var(--sk-primary-border);
}

.sidebar-brand img {
    width: 52px;
    height: 52px;
    object-fit: contain;
}

.sidebar-brand span {
    display: block;
    color: var(--sk-muted);
    font-size: 12px;
    font-weight: 700;
    text-transform: uppercase;
}

.sidebar-brand strong {
    display: block;
    color: var(--sk-primary-dark);
    font-size: 16px;
    line-height: 1.2;
}

.sidebar .nav {
    gap: 6px;
}

.sidebar a {
    color: #334155;
    padding: 11px 12px;
    display: block;
    text-decoration: none;
    border-radius: 8px;
    border: 1px solid transparent;
    font-size: 14px;
    font-weight: 700;
    transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}

.sidebar a:hover,
.sidebar a.active {
    background: var(--sk-primary-soft);
    color: var(--sk-primary-dark);
    border-color: var(--sk-primary-border);
}

.sidebar a.nav-back {
    margin-top: 12px;
    color: var(--sk-primary);
    background: #f0f9ff;
    border-color: var(--sk-accent);
}

.main-content {
    margin-left: 16.666667%;
    padding: 28px 34px 34px;
    min-height: 100vh;
}

.guide-hero {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 320px;
    gap: 24px;
    align-items: stretch;
    padding: 30px;
    margin-bottom: 22px;
    background: var(--sk-surface);
    border: 1px solid var(--sk-primary-border);
    border-radius: 12px;
    box-shadow: 0 16px 38px rgba(31, 41, 55, 0.08);
}

.eyebrow {
    margin: 0 0 8px;
    color: var(--sk-primary);
    font-size: 12px;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.guide-hero h1 {
    margin: 0 0 12px;
    color: var(--sk-primary-dark);
    font-size: 42px;
    line-height: 1.08;
    font-weight: 800;
    border: 0;
    padding: 0;
}

.guide-hero p {
    max-width: 850px;
    margin: 0;
    color: var(--sk-muted);
    font-size: 16px;
}

.hero-panel {
    display: grid;
    gap: 10px;
}

.hero-panel div {
    padding: 14px 16px;
    background: #f7fbff;
    border: 1px solid var(--sk-primary-border);
    border-radius: 10px;
}

.hero-panel span,
.summary-card span {
    display: block;
    color: var(--sk-muted);
    font-size: 12px;
    font-weight: 800;
    text-transform: uppercase;
}

.hero-panel strong {
    display: block;
    margin-top: 4px;
    color: var(--sk-primary-dark);
    font-size: 18px;
}

.guide-summary {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 14px;
    margin-bottom: 24px;
}

.summary-card {
    background: var(--sk-surface);
    border: 1px solid var(--sk-primary-border);
    border-radius: 10px;
    padding: 16px;
    box-shadow: 0 10px 24px rgba(31, 41, 55, 0.05);
}

.summary-card strong {
    display: block;
    margin: 5px 0 6px;
    color: var(--sk-primary-dark);
    font-size: 16px;
}

.summary-card p {
    margin: 0;
    color: var(--sk-muted);
    font-size: 13px;
}

.grade-content {
    display: none;
}

.grade-content.active {
    display: block;
}

.section {
    margin-bottom: 22px;
    padding: 24px;
    background: var(--sk-surface);
    border: 1px solid var(--sk-primary-border);
    border-radius: 12px;
    box-shadow: 0 12px 28px rgba(31, 41, 55, 0.06);
}

.section h2 {
    color: var(--sk-primary-dark);
    font-size: 22px;
    font-weight: 800;
    margin: 0 0 14px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--sk-primary-border);
}

.section h5 {
    color: var(--sk-text);
    font-weight: 800;
}

.section p,
.section li {
    color: var(--sk-muted);
}

.example {
    background: var(--sk-primary-soft);
    padding: 14px 16px;
    border-left: 4px solid var(--sk-accent);
    border-radius: 8px;
    margin-top: 12px;
    color: var(--sk-primary-dark);
}

.grade-table {
    width: 100%;
    margin: 16px 0 6px;
    border-collapse: separate;
    border-spacing: 0;
    border: 1px solid var(--sk-primary-border);
    border-radius: 10px;
    overflow: hidden;
    background: var(--sk-surface);
}

.grade-table th {
    background: var(--sk-primary);
    color: var(--sk-surface);
    padding: 12px 10px;
    text-align: left;
    font-size: 13px;
    text-transform: uppercase;
}

.grade-table td {
    padding: 11px 10px;
    text-align: left;
    border-bottom: 1px solid var(--sk-primary-border);
    color: #334155;
    vertical-align: top;
}

.grade-table tbody tr:nth-child(even) {
    background: #f7fbff;
}

.grade-table tbody tr:last-child td {
    border-bottom: 0;
}

.card {
    border: 1px solid var(--sk-primary-border);
    border-radius: 10px;
    box-shadow: none;
}

.card-header {
    background: var(--sk-primary) !important;
    color: var(--sk-surface) !important;
    border: 0;
    border-radius: 10px 10px 0 0 !important;
}

.card-header h4 {
    font-size: 17px;
    font-weight: 800;
}

.card-body {
    color: var(--sk-muted);
}

footer {
    padding: 18px 0 4px;
}

footer a {
    color: var(--sk-primary);
    font-weight: 700;
}

@media (max-width: 991px) {
    .sidebar {
        position: relative;
        min-height: auto;
        width: 100%;
        padding: 16px;
    }

    .sidebar .nav {
        display: grid;
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .main-content {
        margin-left: 0;
        padding: 20px 16px 28px;
    }

    .guide-hero {
        grid-template-columns: 1fr;
    }

    .guide-summary {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (min-width: 768px) and (max-width: 991px) {
    .sidebar {
        position: fixed;
        width: 25%;
        min-height: 100vh;
    }

    .sidebar .nav {
        display: flex;
    }

    .main-content {
        margin-left: 25%;
        max-width: 75%;
    }
}

@media (max-width: 640px) {
    .guide-hero {
        padding: 22px;
    }

    .guide-hero h1 {
        font-size: 34px;
    }

    .guide-summary,
    .sidebar .nav {
        grid-template-columns: 1fr;
    }

    .section {
        padding: 18px;
    }

    .grade-table {
        display: block;
        overflow-x: auto;
        white-space: nowrap;
    }
}