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

:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #dbeafe;
    --danger: #ef4444;
    --danger-hover: #dc2626;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --radius: 8px;
    --radius-lg: 12px;
    --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px rgba(0,0,0,0.1), 0 4px 6px rgba(0,0,0,0.05);
    --transition: 0.2s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
    background: var(--gray-50);
    color: var(--gray-800);
    line-height: 1.6;
    min-height: 100vh;
}

/* ===== Header ===== */
.header {
    text-align: center;
    padding: 32px 16px 16px;
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: var(--gray-900);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.logo-icon {
    color: var(--primary);
}

.subtitle {
    font-size: 14px;
    color: var(--gray-500);
    margin-top: 4px;
}

/* ===== Tabs ===== */
.tabs {
    display: flex;
    justify-content: center;
    gap: 4px;
    padding: 0 16px;
    margin: 16px auto;
    max-width: 600px;
    background: var(--gray-200);
    border-radius: var(--radius-lg);
    padding: 4px;
}

.tab {
    flex: 1;
    padding: 10px 16px;
    border: none;
    background: transparent;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-600);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    transition: all var(--transition);
    white-space: nowrap;
}

.tab:hover {
    color: var(--gray-800);
    background: rgba(255,255,255,0.5);
}

.tab.active {
    background: white;
    color: var(--primary);
    box-shadow: var(--shadow);
}

.tab svg {
    flex-shrink: 0;
}

/* ===== Container ===== */
.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 0 16px 32px;
}

/* ===== Panels ===== */
.panel {
    display: none;
}

.panel.active {
    display: block;
}

/* ===== Upload Zone ===== */
.upload-zone {
    border: 2px dashed var(--gray-300);
    border-radius: var(--radius-lg);
    padding: 48px 24px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    background: white;
}

.upload-zone:hover,
.upload-zone.dragover {
    border-color: var(--primary);
    background: var(--primary-light);
}

.upload-zone svg {
    color: var(--gray-400);
    margin-bottom: 12px;
}

.upload-zone:hover svg,
.upload-zone.dragover svg {
    color: var(--primary);
}

.upload-text {
    font-size: 16px;
    color: var(--gray-700);
    margin-bottom: 4px;
}

.upload-hint {
    font-size: 13px;
    color: var(--gray-400);
}

/* ===== File List (Merge) ===== */
.file-list {
    margin-top: 16px;
}

.file-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    background: white;
    border-radius: var(--radius);
    margin-bottom: 8px;
    box-shadow: var(--shadow);
    transition: all var(--transition);
    cursor: grab;
    user-select: none;
}

.file-item:active {
    cursor: grabbing;
}

.file-item.dragging {
    opacity: 0.5;
    box-shadow: var(--shadow-lg);
}

.file-item.drag-over {
    border-top: 2px solid var(--primary);
}

.file-item-drag {
    color: var(--gray-400);
    flex-shrink: 0;
    cursor: grab;
}

.file-item-icon {
    flex-shrink: 0;
    color: var(--danger);
}

.file-item-info {
    flex: 1;
    min-width: 0;
}

.file-item-name {
    font-size: 14px;
    font-weight: 500;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-item-meta {
    font-size: 12px;
    color: var(--gray-500);
}

.file-item-remove {
    flex-shrink: 0;
    width: 28px;
    height: 28px;
    border: none;
    background: none;
    border-radius: 50%;
    cursor: pointer;
    color: var(--gray-400);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

.file-item-remove:hover {
    color: var(--danger);
    background: rgba(239,68,68,0.1);
}

/* ===== Buttons ===== */
.actions {
    margin-top: 20px;
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 10px 24px;
    border: none;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    white-space: nowrap;
}

.btn-primary {
    background: var(--primary);
    color: white;
    box-shadow: 0 1px 2px rgba(37,99,235,0.3);
}

.btn-primary:hover {
    background: var(--primary-hover);
    box-shadow: 0 2px 4px rgba(37,99,235,0.4);
}

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-secondary {
    background: white;
    color: var(--gray-700);
    border: 1px solid var(--gray-300);
}

.btn-secondary:hover {
    background: var(--gray-100);
}

.btn-danger {
    background: white;
    color: var(--danger);
    border: 1px solid var(--gray-300);
}

.btn-danger:hover {
    background: rgba(239,68,68,0.05);
    border-color: var(--danger);
}

.btn-sm {
    padding: 6px 12px;
    font-size: 13px;
}

/* ===== Progress ===== */
.progress-container {
    margin-top: 20px;
    text-align: center;
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--gray-200);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 3px;
    width: 0%;
    transition: width 0.3s ease;
}

.progress-text {
    font-size: 13px;
    color: var(--gray-500);
    margin-top: 8px;
}

/* ===== Split Panel ===== */
.split-info,
.manage-info {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.split-info span,
.manage-info span {
    font-size: 14px;
}

#split-filename, #manage-filename {
    font-weight: 600;
    color: var(--gray-800);
}

#split-pagecount, #manage-pagecount {
    color: var(--gray-500);
}

.split-modes {
    display: flex;
    gap: 8px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.radio-card {
    flex: 1;
    min-width: 140px;
    cursor: pointer;
}

.radio-card input[type="radio"] {
    display: none;
}

.radio-card-content {
    display: block;
    padding: 12px 16px;
    background: white;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius);
    transition: all var(--transition);
}

.radio-card-content strong {
    display: block;
    font-size: 14px;
    margin-bottom: 2px;
}

.radio-card-content small {
    font-size: 12px;
    color: var(--gray-500);
}

.radio-card input:checked + .radio-card-content {
    border-color: var(--primary);
    background: var(--primary-light);
}

.split-options {
    margin-bottom: 16px;
}

.split-option label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 6px;
}

.input {
    width: 100%;
    padding: 8px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 14px;
    outline: none;
    transition: border-color var(--transition);
}

.input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.input-hint {
    font-size: 12px;
    color: var(--gray-500);
    margin-top: 4px;
}

/* ===== Page Grid (共用于拆分预览和页面管理) ===== */
.page-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
    gap: 12px;
    margin-bottom: 16px;
}

.page-thumb {
    position: relative;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    cursor: pointer;
    transition: all var(--transition);
    border: 2px solid transparent;
}

.page-thumb:hover {
    box-shadow: var(--shadow-md);
}

.page-thumb.selected {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37,99,235,0.2);
}

.page-thumb-canvas {
    width: 100%;
    aspect-ratio: 210/297;
    display: block;
    background: var(--gray-100);
    object-fit: contain;
}

.page-thumb-label {
    text-align: center;
    padding: 6px 4px;
    font-size: 12px;
    color: var(--gray-600);
    background: var(--gray-50);
}

.page-thumb-checkbox {
    position: absolute;
    top: 6px;
    left: 6px;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: rgba(255,255,255,0.9);
    border: 2px solid var(--gray-300);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

.page-thumb.selected .page-thumb-checkbox {
    background: var(--primary);
    border-color: var(--primary);
}

.page-thumb.selected .page-thumb-checkbox::after {
    content: "";
    width: 6px;
    height: 6px;
    background: white;
    border-radius: 50%;
}

.page-thumb-rotate {
    position: relative;
}

/* ===== Manage Toolbar ===== */
.manage-toolbar {
    margin-bottom: 16px;
}

.manage-actions-bar {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    margin-top: 8px;
}

/* ===== Sortable ===== */
.sortable .page-thumb {
    cursor: grab;
}

.sortable .page-thumb:active {
    cursor: grabbing;
}

.sortable .page-thumb.drag-source {
    opacity: 0.4;
}

.sortable .page-thumb.drag-target {
    border-color: var(--primary);
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 24px 16px;
    font-size: 13px;
    color: var(--gray-400);
    border-top: 1px solid var(--gray-200);
    margin-top: 32px;
}

/* ===== Toast ===== */
.toast-container {
    position: fixed;
    top: 16px;
    right: 16px;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.toast {
    padding: 12px 20px;
    background: var(--gray-800);
    color: white;
    border-radius: var(--radius);
    font-size: 14px;
    box-shadow: var(--shadow-lg);
    animation: slideIn 0.3s ease;
    max-width: 360px;
}

.toast.error {
    background: var(--danger);
}

.toast.success {
    background: #10b981;
}

@keyframes slideIn {
    from { transform: translateX(100%); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

/* ===== 加载占位 ===== */
.page-thumb-loading {
    width: 100%;
    aspect-ratio: 210/297;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gray-100);
    color: var(--gray-400);
    font-size: 13px;
}

/* ===== 响应式 ===== */
@media (max-width: 640px) {
    .header {
        padding: 20px 16px 12px;
    }

    .logo {
        font-size: 20px;
    }

    .tabs {
        margin: 12px 8px;
    }

    .tab {
        padding: 8px 10px;
        font-size: 13px;
    }

    .tab svg {
        display: none;
    }

    .upload-zone {
        padding: 32px 16px;
    }

    .page-grid {
        grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
        gap: 8px;
    }

    .split-modes {
        flex-direction: column;
    }

    .manage-actions-bar {
        gap: 4px;
    }

    .btn-sm {
        padding: 5px 8px;
        font-size: 12px;
    }
}