:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --success: #16a34a;
    --success-dark: #15803d;
    --danger: #dc2626;
    --border: #d1d5db;
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Sarabun", Tahoma, Arial, sans-serif;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
}

.app {
    max-width: 960px;
    margin: 0 auto;
    padding: 24px 16px 64px;
}

.app-header h1 {
    margin: 0 0 4px;
    font-size: 1.6rem;
}

.subtitle {
    margin: 0 0 20px;
    color: var(--text-muted);
    font-size: 0.95rem;
}

.dropzone {
    border: 2px dashed var(--border);
    border-radius: 12px;
    background: var(--card-bg);
    padding: 32px 16px;
    text-align: center;
    transition: border-color .15s, background .15s;
}

.dropzone.dragover {
    border-color: var(--primary);
    background: #eff6ff;
}

.dropzone-icon {
    font-size: 2rem;
    margin-bottom: 8px;
}

.hint {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-top: 8px;
}

.btn {
    display: inline-block;
    border: none;
    border-radius: 8px;
    padding: 10px 18px;
    font-size: 0.95rem;
    cursor: pointer;
    font-weight: 600;
    transition: background .15s, opacity .15s;
}

.btn:disabled { opacity: .5; cursor: not-allowed; }

.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--primary-dark); }

.btn-success { background: var(--success); color: #fff; }
.btn-success:hover:not(:disabled) { background: var(--success-dark); }

.btn-outline { background: transparent; color: var(--text); border: 1px solid var(--border); }
.btn-outline:hover:not(:disabled) { background: #f1f5f9; }

.upload-status {
    margin-top: 12px;
    font-size: 0.9rem;
}

.upload-status .error { color: var(--danger); }
.upload-status .ok { color: var(--success-dark); }

.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 24px;
    padding: 12px 16px;
    background: var(--card-bg);
    border-radius: 10px;
    border: 1px solid var(--border);
}

.toolbar-info { color: var(--text-muted); font-size: 0.9rem; }
.toolbar-actions { display: flex; gap: 8px; flex-wrap: wrap; }

.drag-hint {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin: 14px 2px 6px;
}

.pages-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
    gap: 12px;
    margin-top: 8px;
}

.page-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 10px;
    cursor: grab;
    position: relative;
    user-select: none;
}

.page-card:active { cursor: grabbing; }

.page-card.sortable-ghost { opacity: 0.35; }
.page-card.sortable-chosen { box-shadow: 0 0 0 2px var(--primary); }

.page-preview {
    aspect-ratio: 3 / 4;
    background: #eef2f7;
    border: 1px solid var(--border);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.6rem;
    font-weight: 700;
    color: #94a3b8;
    transition: transform .2s;
    overflow: hidden;
}

.page-preview img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    background: #fff;
    pointer-events: none;
}

.page-file-name {
    font-size: 0.72rem;
    color: var(--text-muted);
    margin: 8px 0 2px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.page-label {
    font-size: 0.78rem;
    font-weight: 600;
}

.page-card-actions {
    display: flex;
    justify-content: space-between;
    margin-top: 8px;
    gap: 4px;
}

.icon-btn {
    flex: 1;
    border: 1px solid var(--border);
    background: #fff;
    border-radius: 6px;
    padding: 5px 0;
    cursor: pointer;
    font-size: 0.95rem;
    line-height: 1;
}

.icon-btn:hover { background: #f1f5f9; }
.icon-btn.remove { color: var(--danger); }

.empty-state {
    grid-column: 1 / -1;
    text-align: center;
    color: var(--text-muted);
    padding: 24px;
}

.app-footer {
    margin-top: 40px;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.8rem;
}

@media (max-width: 480px) {
    .pages-grid { grid-template-columns: repeat(auto-fill, minmax(110px, 1fr)); }
}