/* ─── Design tokens ────────────────────────────────────────── */
:root {
    --blue:        #004065;
    --blue-dark:   #002a42;
    --blue-mid:    #005588;
    --gold:        #FFD200;
    --gold-dark:   #c8a800;
    --text:        #1a1a2e;
    --text-muted:  #5a6a7a;
    --surface:     #ffffff;
    --border:      rgba(0, 64, 101, 0.10);
    --shadow-sm:   0 1px 3px rgba(0,0,0,0.07), 0 4px 12px rgba(0,0,0,0.05);
    --shadow-md:   0 4px 16px rgba(0,0,0,0.10), 0 12px 32px rgba(0,0,0,0.07);
    --shadow-lg:   0 8px 32px rgba(0,0,0,0.13), 0 24px 48px rgba(0,0,0,0.08);
    --radius:      14px;
    --radius-sm:   8px;
    --transition:  0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ─── Reset ────────────────────────────────────────────────── */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* ─── Page background ──────────────────────────────────────── */
html {
    min-height: 100%;
    background:
        radial-gradient(ellipse 80% 60% at 10% 5%,  rgba(0, 64, 101, 0.22) 0%, transparent 65%),
        radial-gradient(ellipse 65% 50% at 90% 95%, rgba(255, 210, 0, 0.18) 0%, transparent 60%),
        linear-gradient(150deg, #e8f2fa 0%, #f5f9fd 45%, #fdf9ee 100%);
}

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background: transparent;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ─── Hero ─────────────────────────────────────────────────── */
.hero {
    background:
        radial-gradient(ellipse 60% 80% at 100% 50%, rgba(255,210,0,0.12) 0%, transparent 60%),
        linear-gradient(135deg, var(--blue-dark) 0%, var(--blue) 55%, var(--blue-mid) 100%);
    padding: 3.5rem 2rem 3rem;
    position: relative;
    overflow: hidden;
}

/* subtle noise texture overlay */
.hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)' opacity='0.035'/%3E%3C/svg%3E");
    pointer-events: none;
    opacity: 0.4;
}

.hero-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 2.5rem;
    position: relative;
    z-index: 1;
}

.hero-logo {
    width: 80px;
    height: auto;
    flex-shrink: 0;
    filter: drop-shadow(0 2px 12px rgba(0,0,0,0.25));
}

.hero-eyebrow {
    font-size: 0.78rem;
    font-weight: 500;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--gold);
    margin-bottom: 0.6rem;
    opacity: 0.9;
}

.hero h1 {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 700;
    line-height: 1.15;
    color: #ffffff;
    letter-spacing: -0.02em;
    margin-bottom: 0.75rem;
}

.hero-sub {
    font-size: 1rem;
    font-weight: 400;
    color: rgba(255,255,255,0.7);
    margin-bottom: 0.35rem;
}

.hero-instructor {
    font-size: 1rem;
    color: rgba(255,255,255,0.65);
}

.instructor-link,
.instructor-link:visited {
    color: var(--gold);
    text-decoration: none;
    font-weight: 500;
    transition: opacity var(--transition);
}

.instructor-link:hover {
    opacity: 0.8;
    text-decoration: underline;
}

/* ─── Main content wrapper ─────────────────────────────────── */
.main-content {
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
    padding: 2.5rem 2rem 3rem;
    flex: 1;
}

/* ─── Overview strip ───────────────────────────────────────── */
.overview {
    background: var(--surface);
    border: 1px solid var(--border);
    border-left: 4px solid var(--gold);
    border-radius: var(--radius-sm);
    padding: 1.1rem 1.4rem;
    margin-bottom: 2.5rem;
    box-shadow: var(--shadow-sm);
    color: var(--text-muted);
    font-size: 0.95rem;
    line-height: 1.7;
}

/* ─── Section label ────────────────────────────────────────── */
.section-label {
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--blue);
    margin-bottom: 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.section-label::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border);
}

/* ─── Lecture grid ─────────────────────────────────────────── */
.lecture-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
}

/* ─── Lecture card ─────────────────────────────────────────── */
.lecture-card {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    text-decoration: none;
    color: inherit;
    overflow: hidden;
    transition:
        transform var(--transition),
        box-shadow var(--transition),
        border-color var(--transition);
    position: relative;
}

.lecture-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(0, 64, 101, 0.22);
}

.lecture-card:hover .card-accent {
    opacity: 1;
}

.lecture-card:hover .arrow {
    transform: translateX(4px);
}

/* gold top accent bar */
.card-accent {
    height: 4px;
    background: linear-gradient(90deg, var(--gold) 0%, var(--gold-dark) 100%);
    opacity: 0.55;
    transition: opacity var(--transition);
}

.card-body {
    padding: 1.4rem 1.4rem 1rem;
    flex: 1;
}

.card-number {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.1em;
    color: var(--blue);
    background: rgba(0, 64, 101, 0.08);
    border-radius: 4px;
    padding: 0.2rem 0.55rem;
    margin-bottom: 0.75rem;
}

.lecture-card h3 {
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.35;
    color: var(--text);
    margin-bottom: 0.6rem;
    letter-spacing: -0.01em;
}

.card-body p {
    font-size: 0.855rem;
    color: var(--text-muted);
    line-height: 1.65;
}

.card-footer {
    padding: 0.9rem 1.4rem 1.1rem;
    border-top: 1px solid var(--border);
    margin-top: auto;
}

.card-cta {
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--blue);
    letter-spacing: 0.01em;
    display: flex;
    align-items: center;
    gap: 0.3rem;
}

.arrow {
    display: inline-block;
    transition: transform var(--transition);
}

/* ─── Footer ───────────────────────────────────────────────── */
.site-footer {
    border-top: 1px solid var(--border);
    padding: 1.25rem 2rem;
    background: rgba(255,255,255,0.5);
    backdrop-filter: blur(8px);
}

.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.6rem;
    font-size: 0.82rem;
    color: var(--text-muted);
}

.footer-sep {
    color: var(--gold-dark);
    font-weight: 700;
}

/* ─── Responsive ───────────────────────────────────────────── */
@media (max-width: 1024px) {
    .lecture-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 640px) {
    .hero {
        padding: 2.5rem 1.25rem 2.25rem;
    }

    .hero-inner {
        flex-direction: column;
        align-items: flex-start;
        gap: 1.25rem;
    }

    .hero-logo {
        width: 60px;
    }

    .main-content {
        padding: 1.75rem 1.25rem 2.5rem;
    }

    .lecture-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }

    .footer-inner {
        flex-wrap: wrap;
        justify-content: center;
        gap: 0.4rem;
    }
}