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

:root {
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-text: #1e293b;
    --color-text-secondary: #64748b;
    --color-border: #e2e8f0;
    --color-danger: #ef4444;
    --color-success: #22c55e;
    --radius: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --max-width: 900px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ===== Layout ===== */
.container { max-width: var(--max-width); margin: 0 auto; padding: 0 16px; }

header {
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: 16px 0;
    box-shadow: var(--shadow);
}
header .container { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 12px; }
header h1 a { color: var(--color-text); font-size: 1.25rem; }
header h1 a:hover { text-decoration: none; }
nav a { margin-left: 16px; font-size: 0.9rem; color: var(--color-text-secondary); }
nav a:hover { color: var(--color-primary); text-decoration: none; }

main { padding: 24px 0; min-height: calc(100vh - 160px); }

footer { text-align: center; padding: 24px 0; color: var(--color-text-secondary); font-size: 0.85rem; border-top: 1px solid var(--color-border); }

/* ===== Search ===== */
.search-box { display: flex; gap: 8px; margin-bottom: 20px; }
.search-box input { flex: 1; padding: 10px 14px; border: 1px solid var(--color-border); border-radius: var(--radius); font-size: 1rem; }
.search-box button { padding: 10px 20px; background: var(--color-primary); color: #fff; border: none; border-radius: var(--radius); cursor: pointer; font-size: 0.95rem; }
.search-box button:hover { background: var(--color-primary-dark); }

/* ===== Loading / Messages ===== */
.loading { text-align: center; padding: 40px; color: var(--color-text-secondary); }
.msg { padding: 10px 14px; border-radius: var(--radius); margin-bottom: 16px; font-size: 0.9rem; }
.msg.error { background: #fee2e2; color: #991b1b; }
.msg.success { background: #dcfce7; color: #166534; }

/* ===== Subject (level 1) ===== */
.subject-details {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    margin-bottom: 8px;
    box-shadow: var(--shadow);
    overflow: hidden;
}
.subject-details[open] { box-shadow: 0 2px 8px rgba(0,0,0,0.1); }

.subject-summary {
    display: flex; justify-content: space-between; align-items: center;
    padding: 16px 20px; cursor: pointer; list-style: none; user-select: none;
    transition: background 0.15s;
}
.subject-summary::-webkit-details-marker { display: none; }
.subject-summary::marker { display: none; }
.subject-summary:hover { background: #f1f5f9; }

.subject-summary::before {
    content: '▸'; display: inline-block; margin-right: 12px;
    font-size: 1.1rem; color: var(--color-text-secondary); transition: transform 0.2s;
}
.subject-details[open] > .subject-summary::before { transform: rotate(90deg); }

.subject-title { font-size: 1.05rem; font-weight: 600; flex: 1; }
.subject-badge {
    background: #e0e7ff; color: #3730a3; padding: 4px 10px;
    border-radius: 12px; font-size: 0.8rem; white-space: nowrap; margin-left: 12px;
}

.subject-content { padding: 0 16px 16px; border-top: 1px solid var(--color-border); }

/* ===== Lecture (level 2) ===== */
.lecture-details {
    margin: 4px 0 4px 12px;
    border: 1px solid var(--color-border);
    border-radius: 6px;
    background: #f8fafc;
    overflow: hidden;
}
.lecture-details[open] { background: #fff; }

.lecture-summary {
    display: flex; justify-content: space-between; align-items: center;
    padding: 12px 16px; cursor: pointer; list-style: none; user-select: none;
    font-size: 0.95rem; transition: background 0.15s;
}
.lecture-summary::-webkit-details-marker { display: none; }
.lecture-summary::marker { display: none; }
.lecture-summary:hover { background: #e2e8f0; }

.lecture-summary::before {
    content: '▸'; display: inline-block; margin-right: 8px;
    font-size: 0.9rem; color: var(--color-text-secondary); transition: transform 0.2s;
}
.lecture-details[open] > .lecture-summary::before { transform: rotate(90deg); }

.lecture-title { font-weight: 500; flex: 1; }
.lecture-meta { color: var(--color-text-secondary); font-size: 0.8rem; margin-left: 12px; }

.lecture-content { padding: 12px 16px; border-top: 1px solid var(--color-border); }

/* ===== Download Button ===== */
.download-btn {
    display: inline-flex; align-items: center; gap: 6px;
    padding: 8px 14px; margin-bottom: 12px;
    background: var(--color-primary); color: #fff;
    border: none; border-radius: 6px; cursor: pointer;
    font-size: 0.85rem; font-weight: 500; transition: background 0.15s;
}
.download-btn:hover { background: var(--color-primary-dark); }
.download-btn:disabled { background: var(--color-text-secondary); cursor: wait; }

/* ===== File Groups (level 3) ===== */
.file-group { padding: 8px 0; }
.file-group:not(:last-child) { border-bottom: 1px dashed var(--color-border); }

.file-group-title {
    font-weight: 600; font-size: 0.9rem; margin-bottom: 8px; color: var(--color-text);
}

.file-link {
    display: block; padding: 4px 0; color: var(--color-primary);
    text-decoration: none; font-size: 0.88rem;
}
.file-link:hover { color: var(--color-primary-dark); text-decoration: underline; }
.file-size { color: var(--color-text-secondary); font-size: 0.78rem; margin-left: 4px; }

/* ===== Mini Gallery ===== */
.mini-gallery {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 8px; margin-top: 4px;
}
.mini-gallery img {
    width: 100%; height: auto; border-radius: 4px;
    border: 1px solid var(--color-border); cursor: pointer;
    transition: transform 0.15s;
}
.mini-gallery img:hover { transform: scale(1.03); }

/* ===== Markdown Body ===== */
.markdown-body { line-height: 1.75; }
.markdown-body h1, .markdown-body h2, .markdown-body h3 { margin: 20px 0 8px; }
.markdown-body h1 { font-size: 1.5rem; border-bottom: 1px solid var(--color-border); padding-bottom: 8px; }
.markdown-body h2 { font-size: 1.25rem; border-bottom: 1px solid var(--color-border); padding-bottom: 6px; }
.markdown-body h3 { font-size: 1.1rem; }
.markdown-body p { margin-bottom: 12px; }
.markdown-body ul, .markdown-body ol { padding-left: 24px; margin-bottom: 12px; }
.markdown-body code { background: #f1f5f9; padding: 2px 6px; border-radius: 4px; font-size: 0.9em; }
.markdown-body pre { background: #1e293b; color: #e2e8f0; padding: 16px; border-radius: var(--radius); overflow-x: auto; margin-bottom: 12px; }
.markdown-body pre code { background: none; padding: 0; color: inherit; }
.markdown-body blockquote { border-left: 4px solid var(--color-primary); padding-left: 16px; color: var(--color-text-secondary); margin-bottom: 12px; }
.markdown-body table { border-collapse: collapse; width: 100%; margin-bottom: 12px; }
.markdown-body th, .markdown-body td { border: 1px solid var(--color-border); padding: 8px 12px; text-align: left; }
.markdown-body th { background: #f1f5f9; }
.markdown-body a { color: var(--color-primary); }
.markdown-body img { max-width: 100%; height: auto; border-radius: 4px; }

/* ===== Modal ===== */
.modal-overlay {
    position: fixed; inset: 0; background: rgba(0,0,0,0.5);
    display: flex; align-items: center; justify-content: center;
    z-index: 1000; padding: 20px;
}
.modal-content {
    background: var(--color-surface); border-radius: var(--radius);
    width: 100%; max-width: 800px; max-height: 90vh;
    display: flex; flex-direction: column;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
}
.modal-header {
    display: flex; justify-content: space-between; align-items: center;
    padding: 16px 20px; border-bottom: 1px solid var(--color-border);
}
.modal-header h3 { font-size: 1.1rem; flex: 1; margin: 0; }
.modal-actions { display: flex; align-items: center; gap: 12px; }
.modal-close {
    background: none; border: none; font-size: 1.8rem; cursor: pointer;
    color: var(--color-text-secondary); padding: 0 4px; line-height: 1;
}
.modal-close:hover { color: var(--color-text); }
#mdModalBody {
    padding: 20px; overflow-y: auto; max-height: calc(90vh - 70px);
}

/* ===== Admin ===== */
.login-form { max-width: 360px; margin: 60px auto; }
.admin-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 24px; }

.card {
    background: var(--color-surface); border: 1px solid var(--color-border);
    border-radius: var(--radius); padding: 20px; margin-bottom: 16px;
    box-shadow: var(--shadow);
}
.card h3 { margin-bottom: 12px; font-size: 1rem; }

.form-group { margin-bottom: 16px; }
.form-group label { display: block; margin-bottom: 4px; font-weight: 500; font-size: 0.9rem; }
.form-group input, .form-group textarea, .form-group select {
    width: 100%; padding: 8px 12px; border: 1px solid var(--color-border);
    border-radius: var(--radius); font-size: 0.95rem;
}
.form-group textarea { min-height: 60px; resize: vertical; }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }

.inline-form { display: flex; gap: 8px; margin-top: 12px; }
.inline-form input { flex: 1; padding: 8px 12px; border: 1px solid var(--color-border); border-radius: var(--radius); font-size: 0.95rem; }

/* Subject list */
.subject-list { max-height: 200px; overflow-y: auto; margin-bottom: 8px; }
.subject-item {
    display: flex; align-items: center; padding: 8px 12px; gap: 8px;
    border: 1px solid var(--color-border); border-radius: 6px; margin-bottom: 4px;
    background: #f8fafc;
}
.subject-name { font-weight: 500; flex: 1; }
.subject-count { color: var(--color-text-secondary); font-size: 0.8rem; }

/* Lecture list */
.lecture-list { max-height: 300px; overflow-y: auto; margin-bottom: 12px; }
.lecture-item {
    display: flex; align-items: center; padding: 8px 12px; gap: 8px;
    border: 1px solid var(--color-border); border-radius: 6px; margin-bottom: 4px;
    background: #f8fafc;
}
.lecture-info { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; flex: 1; }
.lecture-subj-badge {
    background: #e0e7ff; color: #3730a3; padding: 2px 8px; border-radius: 10px;
    font-size: 0.75rem; white-space: nowrap;
}
.lecture-date { color: var(--color-text-secondary); font-size: 0.8rem; }
.lecture-files { color: var(--color-text-secondary); font-size: 0.8rem; }
.lecture-actions { display: flex; gap: 4px; flex-shrink: 0; }

/* Create lecture */
.create-lecture-details { margin-top: 8px; }
.create-lecture-summary {
    cursor: pointer; font-weight: 500; padding: 8px 12px; color: var(--color-primary);
    list-style: none; user-select: none;
}
.create-lecture-summary::-webkit-details-marker { display: none; }
.create-lecture-summary::before { content: ''; }
.create-lecture-details[open] > .create-lecture-summary::after { content: ''; }

.btn {
    display: inline-block; padding: 8px 16px; border: none; border-radius: var(--radius);
    cursor: pointer; font-size: 0.9rem; font-weight: 500; transition: background 0.2s;
}
.btn-primary { background: var(--color-primary); color: #fff; }
.btn-primary:hover { background: var(--color-primary-dark); }
.btn-danger { background: var(--color-danger); color: #fff; }
.btn-danger:hover { background: #dc2626; }
.btn-sm { padding: 4px 10px; font-size: 0.8rem; }

.empty { padding: 12px; text-align: center; color: var(--color-text-secondary); font-size: 0.9rem; }

/* ===== Photo Modal (Telegram-style) ===== */
.photo-modal {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    z-index: 9999;
    background: rgba(0, 0, 0, 0.95);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}

.photo-modal-close {
    position: absolute;
    top: 16px;
    right: 20px;
    z-index: 10001;
    background: rgba(0,0,0,0.5);
    color: #fff;
    border: none;
    border-radius: 50%;
    width: 40px;
    height: 40px;
    font-size: 28px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background 0.2s;
}
.photo-modal-close:hover { background: rgba(255,255,255,0.2); }

.photo-modal-nav {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 80px;
    height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 48px;
    color: rgba(255,255,255,0.7);
    cursor: pointer;
    z-index: 10000;
    transition: color 0.2s, background 0.2s;
    user-select: none;
}
.photo-modal-nav:hover { color: #fff; background: rgba(255,255,255,0.05); }
.photo-modal-prev { left: 0; }
.photo-modal-next { right: 0; }

.photo-modal-image-wrap {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.photo-modal-image-wrap img {
    max-width: 100%;
    max-height: 100vh;
    object-fit: contain;
    border-radius: 4px;
    cursor: default;
    pointer-events: none;
}

.photo-modal-counter {
    position: absolute;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    color: rgba(255,255,255,0.7);
    font-size: 14px;
    background: rgba(0,0,0,0.5);
    padding: 6px 14px;
    border-radius: 16px;
    user-select: none;
}

/* ===== Responsive ===== */
@media (max-width: 600px) {
    header .container { flex-direction: column; align-items: flex-start; }
    nav a { margin-left: 0; margin-right: 16px; }
    .form-row { grid-template-columns: 1fr !important; }
    .mini-gallery { grid-template-columns: repeat(auto-fill, minmax(90px, 1fr)); }
    .search-box { flex-direction: column; }
    .subject-summary, .lecture-summary { padding: 12px 14px; }
    .subject-content { padding: 0 12px 12px; }
    .lecture-content { padding: 10px 14px; }

    /* Photo modal mobile */
    .photo-modal-nav {
        width: 60px;
        height: 80px;
        font-size: 32px;
        background: rgba(0,0,0,0.4);
        border-radius: 8px;
        margin-top: 0;
        transform: translateY(-50%);
    }
    .photo-modal-prev {
        left: 8px;
    }
    .photo-modal-next {
        right: 8px;
    }
    .photo-modal-nav:active {
        background: rgba(0,0,0,0.6);
    }
    .photo-modal-close {
        width: 44px;
        height: 44px;
        top: 12px;
        right: 12px;
    }
}