/* Course hub (root landing) */
body.hub-body {
    font-family: 'Inter', sans-serif;
    margin: 0;
    min-height: 100vh;
    color: #292524;
    background: #fafaf9;
    position: relative;
    overflow-x: hidden;
}

html.dark body.hub-body {
    color: #f5f5f4;
    background: #1c1917;
}

.hub-atmosphere {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    background:
        radial-gradient(ellipse 80% 55% at 15% -10%, rgba(99, 102, 241, 0.18), transparent 55%),
        radial-gradient(ellipse 70% 50% at 90% 10%, rgba(14, 165, 233, 0.12), transparent 50%),
        linear-gradient(180deg, #fafaf9 0%, #f5f5f4 45%, #e7e5e4 100%);
}

html.dark .hub-atmosphere {
    background:
        radial-gradient(ellipse 80% 55% at 15% -10%, rgba(99, 102, 241, 0.22), transparent 55%),
        radial-gradient(ellipse 70% 50% at 90% 10%, rgba(14, 165, 233, 0.1), transparent 50%),
        linear-gradient(180deg, #1c1917 0%, #292524 50%, #1c1917 100%);
}

.hub-header {
    position: relative;
    z-index: 10;
    border-bottom: 1px solid rgba(231, 229, 228, 0.9);
    background: rgba(255, 255, 255, 0.72);
    backdrop-filter: blur(10px);
}

html.dark .hub-header {
    border-bottom-color: rgba(68, 64, 60, 0.9);
    background: rgba(28, 25, 23, 0.75);
}

.hub-header-inner {
    max-width: 960px;
    margin: 0 auto;
    padding: 0.75rem 1.25rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

.hub-brand {
    display: flex;
    align-items: center;
    gap: 0.65rem;
}

.hub-brand-mark {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 2.25rem;
    height: 2.25rem;
    border-radius: 0.5rem;
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.04em;
    color: #fff;
    background: #4f46e5;
}

.hub-brand-name {
    margin: 0;
    font-size: 0.95rem;
    font-weight: 700;
    color: #4338ca;
    line-height: 1.2;
}

html.dark .hub-brand-name {
    color: #a5b4fc;
}

.hub-brand-sub {
    margin: 0;
    font-size: 0.7rem;
    color: #78716c;
}

html.dark .hub-brand-sub {
    color: #a8a29e;
}

.hub-theme-btn {
    padding: 0.35rem 0.75rem;
    font-size: 0.8rem;
    font-weight: 500;
    color: #57534e;
    background: #f5f5f4;
    border: 1px solid #e7e5e4;
    border-radius: 0.375rem;
    cursor: pointer;
}

html.dark .hub-theme-btn {
    color: #d6d3d1;
    background: #292524;
    border-color: #44403c;
}

.hub-theme-btn:hover {
    background: #eef2ff;
    color: #312e81;
}

html.dark .hub-theme-btn:hover {
    background: #312e81;
    color: #e0e7ff;
}

.hub-main {
    position: relative;
    z-index: 1;
    max-width: 960px;
    margin: 0 auto;
    padding: 3.5rem 1.25rem 4rem;
}

.hub-intro {
    margin-bottom: 2.5rem;
    max-width: 36rem;
    animation: hub-fade-up 0.55s ease both;
}

.hub-title {
    margin: 0 0 0.75rem;
    font-size: clamp(2.25rem, 5vw, 3.25rem);
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.1;
    color: #1c1917;
}

html.dark .hub-title {
    color: #fafaf9;
}

.hub-lede {
    margin: 0;
    font-size: 1.05rem;
    line-height: 1.55;
    color: #57534e;
}

html.dark .hub-lede {
    color: #a8a29e;
}

.hub-courses {
    display: grid;
    gap: 1.25rem;
}

@media (min-width: 720px) {
    .hub-courses {
        grid-template-columns: 1fr 1fr;
        gap: 1.5rem;
    }
}

.hub-course {
    display: flex;
    flex-direction: column;
    min-height: 100%;
    padding: 1.75rem 1.5rem;
    text-decoration: none;
    color: inherit;
    background: rgba(255, 255, 255, 0.88);
    border: 1px solid #e7e5e4;
    border-radius: 0.75rem;
    box-shadow: 0 1px 2px rgba(28, 25, 23, 0.04);
    transition: transform 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
    animation: hub-fade-up 0.55s ease both;
}

.hub-course:nth-child(2) {
    animation-delay: 0.1s;
}

html.dark .hub-course {
    background: rgba(41, 37, 36, 0.85);
    border-color: #44403c;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.25);
}

.hub-course:hover,
.hub-course:focus-visible {
    transform: translateY(-3px);
    border-color: #a5b4fc;
    box-shadow: 0 12px 28px rgba(67, 56, 202, 0.12);
    outline: none;
}

html.dark .hub-course:hover,
html.dark .hub-course:focus-visible {
    border-color: #6366f1;
    box-shadow: 0 12px 28px rgba(0, 0, 0, 0.35);
}

.hub-course-index {
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    color: #6366f1;
    margin-bottom: 1rem;
}

html.dark .hub-course-index {
    color: #a5b4fc;
}

.hub-course-title {
    margin: 0 0 0.65rem;
    font-size: 1.35rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: #1c1917;
}

html.dark .hub-course-title {
    color: #fafaf9;
}

.hub-course-desc {
    margin: 0;
    flex: 1;
    font-size: 0.95rem;
    line-height: 1.55;
    color: #57534e;
}

html.dark .hub-course-desc {
    color: #a8a29e;
}

.hub-course-cta {
    margin-top: 1.5rem;
    font-size: 0.875rem;
    font-weight: 600;
    color: #4f46e5;
}

html.dark .hub-course-cta {
    color: #a5b4fc;
}

.hub-course:hover .hub-course-cta,
.hub-course:focus-visible .hub-course-cta {
    text-decoration: underline;
    text-underline-offset: 3px;
}

@keyframes hub-fade-up {
    from {
        opacity: 0;
        transform: translateY(12px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@media (prefers-reduced-motion: reduce) {
    .hub-intro,
    .hub-course {
        animation: none;
    }
    .hub-course:hover,
    .hub-course:focus-visible {
        transform: none;
    }
}