:root {
    /* Light Theme Variables */
    --mtuci-blue: #003366;
    --mtuci-blue-light: #0055aa;
    --mtuci-sky: #e6f0ff;
    --bg-gradient: linear-gradient(135deg, #f0f4f8 0%, #ffffff 100%);
    --card-bg: #ffffff;
    --card-shadow: 0 10px 25px -5px rgba(0, 51, 102, 0.08), 0 8px 10px -6px rgba(0, 51, 102, 0.05);
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --border: #e2e8f0;
    --item-bg: #f8fafc;
}

/* Dark Theme Variables */
[data-theme="dark"] {
    --bg-gradient: linear-gradient(135deg, #0f172a 0%, #020617 100%);
    --card-bg: #1e293b;
    --card-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border: #334155;
    --mtuci-sky: rgba(56, 189, 248, 0.1);
    --mtuci-blue: #38bdf8; /* Lighter blue for dark mode visibility */
    --mtuci-blue-light: #7dd3fc;
    --item-bg: #0f172a;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: transparent;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
}

body {
    font-family: "Inter", -apple-system, system-ui, sans-serif;
    background: var(--bg-gradient);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 1200px;
}

/* --- TOGGLE SWITCH --- */
.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

.theme-toggle button {
    background: var(--card-bg);
    border: 1px solid var(--border);
    color: var(--text-primary);
    width: 45px;
    height: 45px;
    border-radius: 12px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    box-shadow: var(--card-shadow);
}

.theme-toggle button:hover {
    border-color: var(--mtuci-blue);
    transform: scale(1.05);
}

.grid, .extra-nav {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 24px;
}

.grid { margin-bottom: 24px; }

.card, .btn-extra {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 24px;
    padding: 45px 30px;
    text-decoration: none;
    color: inherit;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    box-shadow: var(--card-shadow);
    position: relative;
}

.card:hover, .btn-extra:hover {
    transform: translateY(-8px);
    box-shadow: 0 20px 35px -10px rgba(0, 0, 0, 0.2);
    border-color: var(--mtuci-blue-light);
}

.card::before, .btn-extra::before {
    content: "";
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 5px;
    height: 0;
    background: var(--mtuci-blue);
    border-radius: 0 4px 4px 0;
    transition: height 0.3s ease;
}

.card:hover::before, .btn-extra:hover::before { height: 40%; }

.card-icon, .btn-icon { font-size: 3.5rem; margin-bottom: 25px; }

.card-code {
    font-weight: 800;
    color: var(--mtuci-blue);
    font-size: 0.9rem;
    background: var(--mtuci-sky);
    padding: 6px 18px;
    border-radius: 100px;
    margin-bottom: 20px;
    letter-spacing: 0.5px;
}

.card-title, .btn-text {
    font-size: 1.3rem;
    font-weight: 800;
    line-height: 1.3;
    color: var(--text-primary);
}

/* --- ВНУТРЕННИЕ СТРАНИЦЫ --- */
.internal-content {
    background: var(--card-bg);
    padding: 45px;
    border-radius: 32px;
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border);
}

.breadcrumbs {
    margin-bottom: 25px;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-secondary);
    white-space: nowrap;
    overflow-x: auto;
    padding-bottom: 10px;
}

.breadcrumbs a { color: var(--mtuci-blue); text-decoration: none; }
.breadcrumbs .sep { margin: 0 10px; color: var(--border); }

.page-heading {
    font-size: 2.2rem;
    font-weight: 900;
    margin-bottom: 40px;
    color: var(--text-primary);
    line-height: 1.2;
}

.list-group { display: grid; gap: 15px; }

.list-item {
    display: flex; align-items: center; background: var(--item-bg); padding: 22px 30px;
    border-radius: 20px; text-decoration: none; color: var(--text-primary);
    font-weight: 700; font-size: 1.1rem; border: 1px solid var(--border);
}
.list-item:not(.disabled):hover { border-color: var(--mtuci-blue); transform: translateX(10px); background: var(--card-bg); }
.list-item .icon { margin-right: 20px; font-size: 1.5rem; }
.list-item .arrow { margin-left: auto; color: var(--text-secondary); }

.section-title { margin: 45px 0 20px 0; font-size: 1.1rem; font-weight: 800; color: var(--text-secondary); text-transform: uppercase; letter-spacing: 1.5px; }

.file-item {
    display: flex; align-items: center; background: var(--card-bg); padding: 20px 25px;
    border-radius: 16px; text-decoration: none; color: var(--text-primary);
    margin-bottom: 10px; border: 1px solid var(--border);
}
.file-item:hover { background: var(--item-bg); border-color: var(--mtuci-blue); transform: scale(1.01); }
.file-icon { font-size: 1.8rem; margin-right: 20px; }
.file-name { font-weight: 700; flex-grow: 1; font-size: 1.05rem; overflow-wrap: break-word; word-break: break-all; }
.file-size { font-size: 0.75rem; color: var(--mtuci-blue); font-weight: 800; text-transform: uppercase; letter-spacing: 1px; border: 2px solid var(--mtuci-blue); padding: 4px 12px; border-radius: 8px; flex-shrink: 0; }

.empty-msg { padding: 60px; text-align: center; color: var(--text-secondary); font-weight: 600; border: 2px dashed var(--border); border-radius: 24px; }

/* --- МОБИЛЬНАЯ ОПТИМИЗАЦИЯ --- */
@media (max-width: 768px) {
    body { padding: 10px; align-items: flex-start; }
    .container { margin-top: 50px; }
    .grid, .extra-nav { grid-template-columns: 1fr; gap: 15px; }
    .card, .btn-extra { padding: 35px 20px; }
    .internal-content { padding: 25px 15px; border-radius: 20px; }
    .page-heading { font-size: 1.6rem; margin-bottom: 25px; }
    .list-item { padding: 18px 20px; font-size: 1rem; }
    .file-item { padding: 15px; }
    .file-icon { font-size: 1.5rem; margin-right: 12px; }
    .file-name { font-size: 0.95rem; }
    .file-size { padding: 3px 8px; font-size: 0.7rem; }
}