:root {
    --page-bg: #f1f5f9;
    --text-main: #334155;
    --accent-indigo: #6366f1;
    --accent-emerald: #10b981;
    --accent-slate: #0f172a;
    --card-shadow: 0 18px 40px rgba(15, 23, 42, 0.08);
    --card-shadow-soft: 0 10px 24px rgba(15, 23, 42, 0.06);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: "Nunito", sans-serif;
    background:
        radial-gradient(circle at top left, rgba(250, 204, 21, 0.2), transparent 22rem),
        radial-gradient(circle at top right, rgba(96, 165, 250, 0.18), transparent 20rem),
        linear-gradient(180deg, #f8fafc 0%, var(--page-bg) 100%);
    color: var(--text-main);
    min-height: 100vh;
    line-height: 1.65;
}

.font-arabic {
    font-family: "Tajawal", sans-serif;
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    backdrop-filter: blur(14px);
}

.surface-card {
    box-shadow: var(--card-shadow);
}

.nav-topic {
    position: relative;
    overflow: hidden;
    box-shadow: var(--card-shadow-soft);
}

.nav-topic::after {
    content: "";
    position: absolute;
    inset: auto 0 0 0;
    height: 0.25rem;
    opacity: 0;
    transition: opacity 0.25s ease;
}

.nav-topic.active {
    transform: translateY(-3px);
    box-shadow: 0 20px 34px rgba(15, 23, 42, 0.12);
}

.nav-topic.active::after {
    opacity: 1;
}

.nav-topic[data-unit="unit1"]::after {
    background: linear-gradient(90deg, #facc15, #f59e0b);
}

.nav-topic[data-unit="unit2"]::after {
    background: linear-gradient(90deg, #f87171, #ef4444);
}

.nav-topic[data-unit="unit3"]::after {
    background: linear-gradient(90deg, #60a5fa, #2563eb);
}

.nav-topic[data-unit="unit4"]::after {
    background: linear-gradient(90deg, #4ade80, #16a34a);
}

.nav-kicker {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    margin-bottom: 0.5rem;
    padding: 0.25rem 0.6rem;
    border-radius: 9999px;
    font-size: 0.72rem;
    font-weight: 800;
    letter-spacing: 0.04em;
    background: rgba(255, 255, 255, 0.8);
}

.study-compass {
    position: relative;
    overflow: hidden;
    background:
        radial-gradient(circle at top right, rgba(250, 204, 21, 0.22), transparent 18rem),
        radial-gradient(circle at bottom left, rgba(59, 130, 246, 0.14), transparent 20rem),
        linear-gradient(135deg, rgba(255, 255, 255, 0.98), rgba(248, 250, 252, 0.98));
    border: 1px solid rgba(148, 163, 184, 0.2);
}

.study-compass::before {
    content: "";
    position: absolute;
    inset: 0;
    background:
        linear-gradient(90deg, rgba(15, 23, 42, 0.03) 1px, transparent 1px),
        linear-gradient(rgba(15, 23, 42, 0.03) 1px, transparent 1px);
    background-size: 22px 22px;
    mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.55), transparent 80%);
    pointer-events: none;
}

.compass-card,
.unit-overview-card {
    position: relative;
    background: rgba(255, 255, 255, 0.82);
    border: 1px solid rgba(203, 213, 225, 0.85);
    border-radius: 1.25rem;
    padding: 1rem;
    box-shadow: var(--card-shadow-soft);
}

.unit-overview {
    margin-top: -2rem;
    margin-bottom: 0.5rem;
    position: relative;
    z-index: 10;
}

.unit-overview-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 1rem;
}

.overview-label {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.8rem;
    font-weight: 900;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--accent-slate);
}

.overview-copy {
    margin-top: 0.6rem;
    color: #475569;
    font-size: 0.98rem;
    line-height: 1.7;
}

.section-flow {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin-top: 0.9rem;
}

.flow-chip {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.45rem 0.8rem;
    border-radius: 9999px;
    background: rgba(255, 255, 255, 0.9);
    border: 1px solid rgba(203, 213, 225, 0.8);
    color: #334155;
    font-size: 0.85rem;
    font-weight: 800;
}

.accordion-trigger {
    border: 0;
    cursor: pointer;
    transition: background-color 0.25s ease, transform 0.2s ease;
}

.accordion-trigger:hover {
    background-color: rgba(255, 255, 255, 0.75);
}

.accordion-trigger[aria-expanded="true"] {
    background:
        linear-gradient(90deg, rgba(254, 240, 138, 0.28), rgba(255, 255, 255, 0.92));
}

.accordion-trigger:focus-visible {
    outline: 3px solid rgba(99, 102, 241, 0.45);
    outline-offset: -3px;
}

.accordion-content {
    max-height: 0;
    overflow: hidden;
    transition:
        max-height 0.4s ease,
        padding-top 0.35s ease,
        padding-bottom 0.35s ease,
        opacity 0.25s ease;
    opacity: 0;
    padding-top: 0;
    padding-bottom: 0;
}

.accordion-content.open {
    opacity: 1;
    padding-top: 1.25rem;
    padding-bottom: 1.25rem;
}

.visual-box {
    background-image:
        repeating-linear-gradient(45deg, #f8fafc 25%, transparent 25%, transparent 75%, #f8fafc 75%, #f8fafc),
        repeating-linear-gradient(45deg, #f8fafc 25%, #ffffff 25%, #ffffff 75%, #f8fafc 75%, #f8fafc);
    background-position: 0 0, 10px 10px;
    background-size: 20px 20px;
    border: 2px dashed #cbd5e1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
    margin-top: 1.5rem;
    margin-bottom: 1.5rem;
}

.visual-box strong {
    color: #0f172a;
}

.grad-light {
    background: linear-gradient(135deg, #fef08a 0%, #facc15 100%);
}

.grad-heat {
    background: linear-gradient(135deg, #fecaca 0%, #f87171 100%);
}

.grad-state {
    background: linear-gradient(135deg, #bfdbfe 0%, #60a5fa 100%);
}

.grad-density {
    background: linear-gradient(135deg, #bbf7d0 0%, #4ade80 100%);
}

.hl-tr {
    border-left: 5px solid var(--accent-indigo);
    border-radius: 0.5rem;
    background-color: #f8fafc;
    padding: 1.5rem;
}

.hl-ar {
    border-right: 5px solid var(--accent-emerald);
    border-radius: 0.5rem;
    background-color: #f0fdf4;
    padding: 1.5rem;
}

.story-badge {
    background-color: #fde047;
    color: #854d0e;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-weight: 700;
    font-size: 0.875rem;
    display: inline-block;
    margin-bottom: 0.5rem;
}

.section-shell {
    position: relative;
}

.section-shell::before {
    content: "";
    position: absolute;
    inset: 1rem;
    border-radius: 2rem;
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.3), transparent);
    pointer-events: none;
}

@media (max-width: 768px) {
    body {
        background:
            radial-gradient(circle at top, rgba(250, 204, 21, 0.15), transparent 18rem),
            linear-gradient(180deg, #f8fafc 0%, var(--page-bg) 100%);
    }

    .visual-box {
        padding: 1.25rem;
    }

    .unit-overview {
        margin-top: -1rem;
    }

    .unit-overview-grid {
        grid-template-columns: 1fr;
    }
}