/* ==========================================================================
   CSS Variables & Design Tokens (Minimalist Craft Architecture)
   ========================================================================== */
:root {
    /* Color Palette - Premium Obsidian Monochromatic */
    --bg-base: #090a0f;
    --bg-surface: #11131a;
    --bg-surface-hover: #161822;

    --border-color: #1f2230;
    --border-color-hover: #3b425e;

    --text-main: #f1f2f6;
    --text-muted: #8e94a8;
    --text-inverse: #090a0f;

    --accent-cyan: #38bdf8;
    --accent-emerald: #10b981;
    --accent-amber: #f59e0b;
    --accent-purple: #a855f7;
    --accent-rose: #f43f5e;
    --accent-indigo: #6366f1;
    --accent-teal: #14b8a6;
    --accent-blue: #3b82f6;
    --accent-fuchsia: #d946ef;
    --accent-lime: #84cc16;
    --accent-orange: #f97316;
    --accent-violet: #8b5cf6;

    /* Typography */
    --font-heading: 'Outfit', system-ui, -apple-system, sans-serif;
    --font-body: 'Inter', system-ui, -apple-system, sans-serif;

    /* Transitions & Shadows */
    --transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
    --shadow-glass: 0 10px 30px rgba(0, 0, 0, 0.5);

    /* Dimensions */
    --max-width: 1200px;
    --header-height: 80px;

    --navbar-bg: rgba(17, 19, 26, 0.6);
}

/* Light Theme Override */
body.light-mode {
    --bg-base: #f8fafc;
    --bg-surface: #ffffff;
    --bg-surface-hover: #f1f5f9;
    --border-color: #e2e8f0;
    --border-color-hover: #94a3b8;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --text-inverse: #ffffff;
    --shadow-glass: 0 10px 30px rgba(15, 23, 42, 0.08);
    --navbar-bg: rgba(255, 255, 255, 0.7);
}

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

html {
    scroll-behavior: smooth;
}

body {
    background-color: var(--bg-base);
    background-image: radial-gradient(ellipse 800px 500px at 50% -10%, rgba(56, 189, 248, 0.08), transparent 60%);
    background-repeat: no-repeat;
    color: var(--text-main);
    font-family: var(--font-body);
    font-size: 1rem;
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

main {
    flex: 1;
}

a {
    color: inherit;
    text-decoration: none;
}

button {
    font-family: inherit;
    color: inherit;
    border: none;
    outline: none;
    background: transparent;
}

/* Glassmorphism / Surface Card Utility */
.glass-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    box-shadow: var(--shadow-glass);
    transition: var(--transition);
}

.glass-card:hover {
    border-color: var(--border-color-hover);
    transform: translateY(-4px);
    box-shadow: 0 20px 45px rgba(0, 0, 0, 0.55);
}

/* Entrance Animation Utility */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(16px); }
    to { opacity: 1; transform: translateY(0); }
}

.fade-in-up {
    animation: fadeInUp 0.7s cubic-bezier(0.16, 1, 0.3, 1) both;
}

/* Typography Utilities */
h1, h2, h3, h4 {
    font-family: var(--font-heading);
    font-weight: 700;
    line-height: 1.15;
    letter-spacing: -0.03em;
}

.text-center { text-align: center; }

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.navbar {
    position: sticky;
    top: 0;
    left: 0;
    width: 100%;
    height: var(--header-height);
    z-index: 1000;
    display: flex;
    align-items: center;
    background: var(--navbar-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
}

.nav-container {
    max-width: var(--max-width);
    width: 100%;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 800;
    letter-spacing: -0.04em;
}

.accent {
    color: var(--accent-cyan);
}

.theme-toggle {
    margin-left: auto;
    font-size: 1.4rem;
    cursor: pointer;
    color: var(--text-main);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 8px;
    border-radius: 8px;
    transition: var(--transition);
}

.theme-toggle:hover {
    background: var(--bg-surface-hover);
}

/* ==========================================================================
   Portal Section (Project Selection)
   ========================================================================== */
.portal {
    min-height: calc(100vh - var(--header-height));
    display: flex;
    align-items: center;
    padding: 60px 0;
}

.portal-container {
    max-width: var(--max-width);
    width: 100%;
    margin: 0 auto;
    padding: 0 24px;
}

.portal-header {
    text-align: center;
    margin-bottom: 56px;
}

.section-subtitle {
    font-family: var(--font-heading);
    color: var(--accent-cyan);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    font-size: 0.75rem;
    display: inline-block;
    margin-bottom: 16px;
    padding: 6px 14px;
    border-radius: 999px;
    background: rgba(56, 189, 248, 0.08);
    border: 1px solid rgba(56, 189, 248, 0.2);
}

.portal-title {
    font-size: 2.75rem;
    letter-spacing: -0.04em;
}

.portal-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 28px;
    max-width: 820px;
    margin: 0 auto;
}

.portal-card {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    padding: 40px 32px;
    gap: 8px;
}

.portal-card-ampel {
    position: absolute;
    top: 16px;
    right: 16px;
    display: flex;
    gap: 6px;
    z-index: 5;
}

.ampel-dot {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    cursor: pointer;
    background: transparent;
    transition: var(--transition);
}

.ampel-dot:hover {
    transform: scale(1.2);
}

.ampel-dot.ampel-rot { border: 1.5px solid rgba(244, 63, 94, 0.5); }
.ampel-dot.ampel-gelb { border: 1.5px solid rgba(245, 158, 11, 0.5); }
.ampel-dot.ampel-gruen { border: 1.5px solid rgba(16, 185, 129, 0.5); }

.ampel-dot.ampel-rot.active { background: #f43f5e; border-color: #f43f5e; box-shadow: 0 0 6px rgba(244, 63, 94, 0.7); }
.ampel-dot.ampel-gelb.active { background: #f59e0b; border-color: #f59e0b; box-shadow: 0 0 6px rgba(245, 158, 11, 0.7); }
.ampel-dot.ampel-gruen.active { background: #10b981; border-color: #10b981; box-shadow: 0 0 6px rgba(16, 185, 129, 0.7); }

.portal-card-icon {
    width: 52px;
    height: 52px;
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.6rem;
    margin-bottom: 16px;
    transition: var(--transition);
}

.portal-card:hover .portal-card-icon {
    transform: scale(1.08);
}

.portal-card-link i {
    transition: transform 0.2s ease;
}

.portal-card:hover .portal-card-link i {
    transform: translateX(3px);
}

.portal-card-icon.icon-cyan {
    background: rgba(56, 189, 248, 0.1);
    border: 1px solid rgba(56, 189, 248, 0.2);
    color: var(--accent-cyan);
}

.portal-card-icon.icon-emerald {
    background: rgba(16, 185, 129, 0.1);
    border: 1px solid rgba(16, 185, 129, 0.2);
    color: var(--accent-emerald);
}

.portal-card-icon.icon-amber {
    background: rgba(245, 158, 11, 0.1);
    border: 1px solid rgba(245, 158, 11, 0.2);
    color: var(--accent-amber);
}

.portal-card-icon.icon-purple {
    background: rgba(168, 85, 247, 0.1);
    border: 1px solid rgba(168, 85, 247, 0.2);
    color: var(--accent-purple);
}

.portal-card-icon.icon-rose {
    background: rgba(244, 63, 94, 0.1);
    border: 1px solid rgba(244, 63, 94, 0.2);
    color: var(--accent-rose);
}

.portal-card-icon.icon-indigo {
    background: rgba(99, 102, 241, 0.1);
    border: 1px solid rgba(99, 102, 241, 0.2);
    color: var(--accent-indigo);
}

.portal-card-icon.icon-teal {
    background: rgba(20, 184, 166, 0.1);
    border: 1px solid rgba(20, 184, 166, 0.2);
    color: var(--accent-teal);
}

.portal-card-icon.icon-blue {
    background: rgba(59, 130, 246, 0.1);
    border: 1px solid rgba(59, 130, 246, 0.2);
    color: var(--accent-blue);
}

.portal-card-icon.icon-fuchsia {
    background: rgba(217, 70, 239, 0.1);
    border: 1px solid rgba(217, 70, 239, 0.2);
    color: var(--accent-fuchsia);
}

.portal-card-icon.icon-lime {
    background: rgba(132, 204, 22, 0.1);
    border: 1px solid rgba(132, 204, 22, 0.2);
    color: var(--accent-lime);
}

.portal-card-icon.icon-orange {
    background: rgba(249, 115, 22, 0.1);
    border: 1px solid rgba(249, 115, 22, 0.2);
    color: var(--accent-orange);
}

.portal-card-icon.icon-violet {
    background: rgba(139, 92, 246, 0.1);
    border: 1px solid rgba(139, 92, 246, 0.2);
    color: var(--accent-violet);
}

.portal-card-title {
    font-size: 1.5rem;
    overflow-wrap: break-word;
    word-break: break-word;
    hyphens: auto;
}

.portal-card-tag {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--text-muted);
}

.portal-card-desc {
    color: var(--text-muted);
    font-size: 0.95rem;
    flex-grow: 1;
}

.portal-card-link {
    margin-top: 16px;
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--text-main);
}

/* ==========================================================================
   Sub-Page Header (z.B. Mathe-Übersicht)
   ========================================================================== */
.page-header {
    margin-bottom: 48px;
}

.page-title {
    font-size: 2rem;
    letter-spacing: -0.03em;
    margin-top: 8px;
}

.page-desc {
    color: var(--text-muted);
    font-size: 1rem;
    margin-top: 10px;
    max-width: 620px;
}

.back-link {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 6px;
    transition: var(--transition);
}

.back-link:hover {
    color: var(--text-main);
}

/* ==========================================================================
   Topics Grid (z.B. Mathe-Übersicht)
   ========================================================================== */
.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 24px;
}

/* ==========================================================================
   Footer
   ========================================================================== */
.footer {
    border-top: 1px solid var(--border-color);
    padding: 60px 0 40px;
}

.footer-container {
    max-width: var(--max-width);
    width: 100%;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 36px;
}

.footer-brand h2 {
    font-size: 2rem;
    margin-bottom: 8px;
}

.footer-brand p {
    color: var(--text-muted);
}

.footer-social {
    display: flex;
    gap: 20px;
}

.social-icon {
    font-size: 1.5rem;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--bg-surface);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.social-icon:hover {
    background: var(--text-main);
    color: var(--bg-base);
    transform: translateY(-2px);
}

.footer-bottom {
    color: var(--text-muted);
    font-size: 0.9rem;
    border-top: 1px solid var(--border-color);
    padding-top: 24px;
    width: 100%;
}

/* ==========================================================================
   Responsive Breakpoints
   ========================================================================== */
@media screen and (max-width: 640px) {
    .portal-title { font-size: 2.1rem; }
    .portal-grid { grid-template-columns: 1fr; }
    .portal-card { padding: 32px 24px; }
    .page-title { font-size: 1.6rem; }
}