/* =============================================
 T EACHER PANEL — Clean Minimalist UI                                        *
 Font: Inter | No external frameworks
 ============================================= */

:root {
    --accent:        #2563eb;
    --accent-hover:  #1d4ed8;
    --accent-light:  #eff6ff;
    --danger:        #ef4444;
    --danger-light:  #fef2f2;
    --success:       #10b981;
    --success-light: #ecfdf5;
    --warn:          #f59e0b;

    --bg:       #f8fafc;
    --surface:  #ffffff;
    --border:   #e2e8f0;
    --border-2: #cbd5e1;

    --txt:      #0f172a;
    --txt-2:    #475569;
    --txt-3:    #94a3b8;

    --radius:   10px;
    --radius-sm:6px;
    --radius-lg:16px;

    --shadow-sm: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
    --shadow:    0 4px 12px rgba(0,0,0,.07);
    --shadow-lg: 0 8px 30px rgba(0,0,0,.10);

    --transition: .15s cubic-bezier(.4,0,.2,1);
    --topbar-h: 56px;
}

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

body {
    font-family: 'Inter', system-ui, sans-serif;
    background: var(--bg);
    color: var(--txt);
    line-height: 1.6;
    font-size: 14px;
    -webkit-font-smoothing: antialiased;
    min-height: 100vh;
}

/* ── Topbar ── */
.topbar {
    position: sticky;
    top: 0;
    z-index: 100;
    height: var(--topbar-h);
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    gap: 0;
    padding: 0 24px;
}

.topbar-logo {
    display: flex;
    align-items: center;
    gap: 9px;
    font-weight: 600;
    font-size: 15px;
    color: var(--txt);
    text-decoration: none;
    white-space: nowrap;
    padding-right: 20px;
    border-right: 1px solid var(--border);
    margin-right: 16px;
}
.topbar-logo svg { color: var(--accent); }

.topbar-breadcrumb {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 13px;
    color: var(--txt-2);
}
.topbar-breadcrumb a {
    color: var(--txt-2);
    text-decoration: none;
    transition: color var(--transition);
}
.topbar-breadcrumb a:hover { color: var(--accent); }
.topbar-breadcrumb .sep { color: var(--txt-3); }

/* ── Page layout ── */
.page {
    max-width: 1200px;
    margin: 0 auto;
    padding: 32px 24px 64px;
}

.page-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 28px;
    flex-wrap: wrap;
}

.page-header h1 {
    font-size: 22px;
    font-weight: 700;
    letter-spacing: -.3px;
    color: var(--txt);
}

.page-header p {
    color: var(--txt-2);
    margin-top: 4px;
    font-size: 13px;
}

.page-actions {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

/* ── Buttons ── */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    border: 1px solid transparent;
    text-decoration: none;
    transition: var(--transition);
    white-space: nowrap;
    line-height: 1;
}
.btn svg { flex-shrink: 0; }

.btn-primary   { background: var(--accent); color: #fff; border-color: var(--accent); }
.btn-primary:hover { background: var(--accent-hover); }

.btn-outline   { background: var(--surface); color: var(--txt); border-color: var(--border-2); }
.btn-outline:hover { background: var(--bg); border-color: var(--accent); color: var(--accent); }

.btn-danger    { background: var(--danger-light); color: var(--danger); border-color: #fecaca; }
.btn-danger:hover { background: var(--danger); color: #fff; }

.btn-ghost     { background: transparent; color: var(--txt-2); border-color: transparent; }
.btn-ghost:hover { background: var(--bg); color: var(--txt); }

.btn-success   { background: var(--success); color: #fff; border-color: var(--success); }
.btn-success:hover { filter: brightness(1.08); }

.btn-icon {
    width: 32px; height: 32px;
    padding: 0;
    display: inline-flex;
    align-items: center; justify-content: center;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--txt-2);
    cursor: pointer;
    transition: var(--transition);
}
.btn-icon:hover { border-color: var(--border-2); color: var(--txt); background: var(--bg); }
.btn-icon.danger:hover { border-color: var(--danger); color: var(--danger); background: var(--danger-light); }

/* ── Toggle ── */
.toggle-wrap {
    display: flex;
    align-items: center;
    gap: 10px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 6px 12px;
    cursor: pointer;
    user-select: none;
}
.toggle {
    position: relative;
    width: 36px; height: 20px;
    background: var(--border-2);
    border-radius: 10px;
    transition: background var(--transition);
    flex-shrink: 0;
    cursor: pointer;
    border: none;
    appearance: none;
}
.toggle::after {
    content: '';
    position: absolute;
    width: 16px; height: 16px;
    background: #fff;
    border-radius: 50%;
    top: 2px; left: 2px;
    transition: left var(--transition);
    box-shadow: 0 1px 3px rgba(0,0,0,.2);
}
.toggle:checked { background: var(--accent); }
.toggle:checked::after { left: 18px; }
.toggle-label { font-size: 13px; font-weight: 500; color: var(--txt); }

/* ── Cards grid ── */
.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 14px;
}

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 20px;
    text-decoration: none;
    color: var(--txt);
    display: block;
    transition: var(--transition);
    position: relative;
    box-shadow: var(--shadow-sm);
}
.card:hover {
    border-color: var(--border-2);
    box-shadow: var(--shadow);
    transform: translateY(-1px);
}

.card-icon {
    width: 42px; height: 42px;
    border-radius: var(--radius-sm);
    background: var(--accent-light);
    color: var(--accent);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 14px;
}

.card-title { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.card-meta  { font-size: 12px; color: var(--txt-2); }

.card-wrapper { position: relative; }
.card-row-actions {
    position: absolute;
    top: 10px; right: 10px;
    display: flex;
    gap: 4px;
    opacity: 0;
    transition: opacity var(--transition);
}
.card-wrapper:hover .card-row-actions { opacity: 1; }

/* ── Empty state ── */
.empty {
    text-align: center;
    padding: 72px 32px;
    background: var(--surface);
    border: 1px dashed var(--border-2);
    border-radius: var(--radius-lg);
    color: var(--txt-2);
}
.empty svg { margin-bottom: 16px; color: var(--txt-3); }
.empty h3 { font-size: 16px; font-weight: 600; color: var(--txt); margin-bottom: 6px; }
.empty p  { font-size: 13px; max-width: 360px; margin: 0 auto; }

/* ── Stat badge ── */
.stat {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    font-size: 12px;
    font-weight: 500;
    color: var(--txt-2);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 3px 10px;
}
.stat-dot {
    width: 6px; height: 6px;
    border-radius: 50%;
    background: var(--txt-3);
}

/* ── Upload zone ── */
.upload-zone {
    border: 2px dashed var(--border-2);
    border-radius: var(--radius-lg);
    background: var(--surface);
    padding: 40px 24px;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    margin-bottom: 24px;
}
.upload-zone:hover,
.upload-zone.drag-over {
    border-color: var(--accent);
    background: var(--accent-light);
}
.upload-zone svg { color: var(--txt-3); margin-bottom: 12px; }
.upload-zone:hover svg { color: var(--accent); }
.upload-zone h3 { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.upload-zone p  { font-size: 13px; color: var(--txt-2); }

.upload-progress {
    margin-top: 16px;
    display: none;
}
.progress-bar {
    height: 4px;
    background: var(--border);
    border-radius: 2px;
    overflow: hidden;
    margin-top: 8px;
}
.progress-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 2px;
    transition: width .3s ease;
    width: 0%;
}

/* ── Gallery grid ── */
.gallery-toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.gallery-search {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 6px 12px;
    flex: 1;
    max-width: 280px;
}
.gallery-search svg { color: var(--txt-3); flex-shrink: 0; }
.gallery-search input {
    border: none;
    outline: none;
    background: transparent;
    font-size: 13px;
    color: var(--txt);
    width: 100%;
}
.gallery-search input::placeholder { color: var(--txt-3); }

.photo-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 10px;
}

.photo-item {
    position: relative;
    aspect-ratio: 1;
    border-radius: var(--radius);
    overflow: hidden;
    cursor: pointer;
    border: 2px solid transparent;
    transition: var(--transition);
    background: var(--border);
}
.photo-item:hover { border-color: var(--accent); }
.photo-item.is-ref { border-color: var(--success); }
.photo-item img {
    width: 100%; height: 100%;
    object-fit: cover;
    display: block;
    transition: transform .2s ease;
}
.photo-item:hover img { transform: scale(1.03); }

.photo-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,.45);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity var(--transition);
    gap: 8px;
}
.photo-item:hover .photo-overlay { opacity: 1; }

.photo-actions {
    position: absolute;
    top: 6px; right: 6px;
    display: flex;
    gap: 4px;
    opacity: 0;
    transition: opacity var(--transition);
}
.photo-item:hover .photo-actions { opacity: 1; }

.photo-btn {
    width: 28px; height: 28px;
    border-radius: 6px;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    backdrop-filter: blur(6px);
    transition: var(--transition);
}
.photo-btn.del { background: rgba(239,68,68,.85); color: #fff; }
.photo-btn.del:hover { background: var(--danger); }
.photo-btn.ref { background: rgba(16,185,129,.85); color: #fff; }
.photo-btn.ref:hover { background: var(--success); }

.photo-name {
    position: absolute;
    bottom: 0; left: 0; right: 0;
    background: linear-gradient(transparent, rgba(0,0,0,.7));
    color: #fff;
    font-size: 11px;
    font-weight: 500;
    padding: 16px 8px 6px;
    opacity: 0;
    transition: opacity var(--transition);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.photo-item:hover .photo-name { opacity: 1; }

.ref-badge {
    position: absolute;
    top: 6px; left: 6px;
    background: var(--success);
    color: #fff;
    font-size: 10px;
    font-weight: 700;
    padding: 2px 6px;
    border-radius: 4px;
    letter-spacing: .3px;
}

/* ── Lightbox ── */
.lightbox {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 1000;
    background: rgba(15,23,42,.92);
    backdrop-filter: blur(4px);
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.lightbox.open { display: flex; }

.lb-close {
    position: absolute;
    top: 16px; right: 16px;
    width: 40px; height: 40px;
    background: rgba(255,255,255,.1);
    border: 1px solid rgba(255,255,255,.15);
    border-radius: 50%;
    color: #fff;
    font-size: 20px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition);
    z-index: 10;
}
.lb-close:hover { background: rgba(255,255,255,.2); }

.lb-body {
    display: flex;
    gap: 16px;
    align-items: flex-start;
    max-width: 95vw;
    max-height: 85vh;
}

.lb-img-col {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    flex: 1;
    max-width: 100%;
}
.lb-label {
    font-size: 12px;
    font-weight: 600;
    color: rgba(255,255,255,.6);
    text-transform: uppercase;
    letter-spacing: .5px;
}
.lb-label.ref { color: #6ee7b7; }

.lb-image {
    max-height: 72vh;
    max-width: 80vw;
    border-radius: var(--radius);
    object-fit: contain;
    border: 1px solid rgba(255,255,255,.1);
}
.lb-body.compare .lb-image { max-width: 44vw; }

.lb-caption {
    font-size: 12px;
    color: rgba(255,255,255,.5);
    text-align: center;
}

.lb-ref-col {
    display: none;
    flex-direction: column;
    align-items: center;
    gap: 10px;
}
.lb-body.compare .lb-ref-col { display: flex; }

.lb-ocr-col {
    display: none;
    flex-direction: column;
    background: var(--surface);
    border-radius: var(--radius);
    padding: 20px;
    width: 360px;
    max-height: 72vh;
    overflow: hidden;
}
.lb-ocr-col.open { display: flex; }
.lb-ocr-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--border);
}
.lb-ocr-header h4 { font-size: 13px; font-weight: 600; }
.lb-ocr-content {
    flex: 1;
    overflow-y: auto;
    font-family: 'SF Mono', 'Fira Code', monospace;
    font-size: 12px;
    line-height: 1.7;
    color: var(--txt);
    white-space: pre-wrap;
}

.lb-nav {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 44px; height: 44px;
    background: rgba(255,255,255,.1);
    border: 1px solid rgba(255,255,255,.15);
    border-radius: 50%;
    color: #fff;
    font-size: 18px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition);
    z-index: 10;
}
.lb-nav:hover { background: rgba(255,255,255,.2); }
.lb-prev { left: 16px; }
.lb-next { right: 16px; }

.lb-bar {
    position: absolute;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
    justify-content: center;
    z-index: 10;
}
.lb-counter {
    font-size: 12px;
    color: rgba(255,255,255,.5);
    background: rgba(255,255,255,.08);
    border-radius: 20px;
    padding: 4px 12px;
}

/* ── Info row ── */
.info-row {
    display: flex;
    gap: 24px;
    align-items: center;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 14px 20px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}
.info-item { display: flex; flex-direction: column; gap: 2px; }
.info-label { font-size: 10px; font-weight: 600; color: var(--txt-3); text-transform: uppercase; letter-spacing: .5px; }
.info-value { font-size: 14px; font-weight: 600; color: var(--txt); }

/* ── Notifications ── */
.toast-wrap {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 2000;
    display: flex;
    flex-direction: column;
    gap: 8px;
    pointer-events: none;
}
.toast {
    background: var(--txt);
    color: #fff;
    font-size: 13px;
    font-weight: 500;
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-lg);
    animation: toastIn .2s ease;
    pointer-events: auto;
}
.toast.success { background: var(--success); }
.toast.error   { background: var(--danger); }
@keyframes toastIn {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ── Responsive ── */
@media (max-width: 768px) {
    .page { padding: 20px 16px 48px; }
    .cards-grid { grid-template-columns: 1fr 1fr; gap: 10px; }
    .photo-grid { grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); }
    .lb-body { flex-direction: column; max-height: 90vh; }
    .lb-image { max-height: 50vh; max-width: 90vw; }
    .lb-body.compare .lb-image { max-width: 90vw; }
    .lb-ocr-col { width: 90vw; }
    .lb-nav { width: 36px; height: 36px; font-size: 14px; }
    .lb-prev { left: 8px; }
    .lb-next { right: 8px; }
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-2); border-radius: 3px; }