/* ===== Design Tokens ===== */
:root {
    --primary: #1e3a8a;
    --primary-light: #2563eb;
    --primary-glow: rgba(37, 99, 235, 0.15);
    --gradient: linear-gradient(135deg, #1e3a8a 0%, #2563eb 100%);
    --gradient-hover: linear-gradient(135deg, #1e3570 0%, #1d4ed8 100%);
    --gradient-subtle: linear-gradient(135deg, rgba(30,58,138,0.04) 0%, rgba(37,99,235,0.06) 100%);
    --gradient-mesh: radial-gradient(ellipse at 20% 50%, rgba(37,99,235,0.08) 0%, transparent 50%),
                     radial-gradient(ellipse at 80% 20%, rgba(30,58,138,0.06) 0%, transparent 50%),
                     radial-gradient(ellipse at 50% 80%, rgba(59,130,246,0.05) 0%, transparent 50%);
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-heading: 'Space Grotesk', 'Inter', sans-serif;
    --white: #ffffff;
    --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;
    --green-50: #f0fdf4;
    --green-100: #dcfce7;
    --green-500: #22c55e;
    --green-600: #16a34a;
    --green-700: #15803d;
    --red-50: #fef2f2;
    --red-100: #fee2e2;
    --red-500: #ef4444;
    --red-600: #dc2626;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
    --shadow-xl: 0 20px 40px -8px rgba(30, 58, 138, 0.18);
    --shadow-glow: 0 0 30px rgba(37, 99, 235, 0.12);
    --sidebar-width: 240px;
    --header-height: 64px;
    --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* ===== Keyframe Animations ===== */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideInLeft {
    from { opacity: 0; transform: translateX(-12px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes scaleIn {
    from { opacity: 0; transform: scale(0.92); }
    to { opacity: 1; transform: scale(1); }
}

@keyframes shimmer {
    0% { background-position: -200% 0; }
    100% { background-position: 200% 0; }
}

@keyframes pulse-ring {
    0% { transform: scale(0.95); opacity: 1; }
    50% { transform: scale(1.05); opacity: 0.7; }
    100% { transform: scale(0.95); opacity: 1; }
}

@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-6px); }
}

@keyframes gradient-shift {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    background: var(--gray-50);
    background-image: var(--gradient-mesh);
    background-attachment: fixed;
    color: var(--gray-800);
    line-height: 1.6;
    min-height: 100vh;
}

/* ===== Header ===== */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.82);
    -webkit-backdrop-filter: blur(16px) saturate(180%);
    backdrop-filter: blur(16px) saturate(180%);
    border-bottom: 1px solid rgba(229, 231, 235, 0.6);
    box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}

.header-inner {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 0 28px;
    height: var(--header-height);
    max-width: 1440px;
    margin: 0 auto;
}

.back-link {
    font-size: 13px;
    color: var(--primary);
    text-decoration: none;
    font-weight: 600;
    white-space: nowrap;
    transition: all 0.25s var(--ease-out-expo);
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    letter-spacing: -0.01em;
}

.back-link:hover {
    color: var(--primary-light);
    background: var(--gradient-subtle);
}

.header-title {
    font-family: var(--font-heading);
    font-size: 22px;
    font-weight: 700;
    color: var(--gray-900);
    flex: 1;
    letter-spacing: -0.03em;
}

.privacy-badge {
    font-size: 12px;
    font-weight: 600;
    color: var(--green-700);
    background: linear-gradient(135deg, rgba(240,253,244,0.9), rgba(220,252,231,0.9));
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(187,247,208,0.5);
    padding: 6px 14px;
    border-radius: 20px;
    white-space: nowrap;
    animation: fadeIn 0.6s var(--ease-out-expo);
}

/* ===== App Layout ===== */
.app-layout {
    display: flex;
    min-height: calc(100vh - var(--header-height));
}

/* ===== Sidebar ===== */
.sidebar {
    width: var(--sidebar-width);
    background: rgba(255,255,255,0.7);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
    border-right: 1px solid rgba(229, 231, 235, 0.5);
    position: sticky;
    top: var(--header-height);
    height: calc(100vh - var(--header-height));
    overflow-y: auto;
    flex-shrink: 0;
}

.sidebar-nav {
    padding: 16px 10px;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.sidebar-item {
    display: flex;
    align-items: center;
    gap: 11px;
    padding: 11px 14px;
    border: none;
    background: none;
    cursor: pointer;
    font-family: var(--font-body);
    font-size: 13.5px;
    font-weight: 500;
    color: var(--gray-600);
    text-align: left;
    transition: all 0.25s var(--ease-out-expo);
    border-radius: var(--radius-sm);
    width: 100%;
    position: relative;
    letter-spacing: -0.01em;
    animation: slideInLeft 0.4s var(--ease-out-expo) both;
}

.sidebar-item:nth-child(1)  { animation-delay: 0.02s; }
.sidebar-item:nth-child(2)  { animation-delay: 0.04s; }
.sidebar-item:nth-child(3)  { animation-delay: 0.06s; }
.sidebar-item:nth-child(4)  { animation-delay: 0.08s; }
.sidebar-item:nth-child(5)  { animation-delay: 0.10s; }
.sidebar-item:nth-child(6)  { animation-delay: 0.12s; }
.sidebar-item:nth-child(7)  { animation-delay: 0.14s; }
.sidebar-item:nth-child(8)  { animation-delay: 0.16s; }
.sidebar-item:nth-child(9)  { animation-delay: 0.18s; }
.sidebar-item:nth-child(10) { animation-delay: 0.20s; }
.sidebar-item:nth-child(11) { animation-delay: 0.22s; }
.sidebar-item:nth-child(12) { animation-delay: 0.24s; }

.sidebar-item:hover {
    background: var(--gradient-subtle);
    color: var(--gray-900);
    transform: translateX(3px);
}

.sidebar-item.active {
    background: var(--gradient);
    color: var(--white);
    font-weight: 600;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.25);
}

.sidebar-item.active .sidebar-icon {
    filter: brightness(10);
}

.sidebar-icon {
    font-size: 17px;
    width: 24px;
    text-align: center;
    flex-shrink: 0;
    transition: transform 0.25s var(--ease-spring);
}

.sidebar-item:hover .sidebar-icon {
    transform: scale(1.15);
}

.sidebar-label {
    white-space: nowrap;
}

.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.4);
    z-index: 199;
}

/* ===== Hamburger ===== */
.hamburger {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 201;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: none;
    background: var(--gradient);
    box-shadow: var(--shadow-lg);
    cursor: pointer;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 5px;
}

.hamburger span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--white);
    border-radius: 2px;
    transition: all 0.3s;
}

.hamburger.open span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.open span:nth-child(2) {
    opacity: 0;
}

.hamburger.open span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* ===== Main Content ===== */
.main-content {
    flex: 1;
    min-width: 0;
    padding: 32px 24px;
}

/* ===== Welcome Screen ===== */
.welcome-screen {
    max-width: 920px;
    margin: 0 auto;
    text-align: center;
    padding-top: 32px;
    animation: fadeIn 0.5s var(--ease-out-expo);
}

.welcome-title {
    font-family: var(--font-heading);
    font-size: 32px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 8px;
    letter-spacing: -0.04em;
    animation: fadeInUp 0.6s var(--ease-out-expo);
}

.welcome-subtitle {
    font-size: 15px;
    color: var(--gray-500);
    margin-bottom: 40px;
    animation: fadeInUp 0.6s 0.08s var(--ease-out-expo) both;
}

.tool-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 14px;
}

.tool-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    padding: 28px 12px 22px;
    background: rgba(255, 255, 255, 0.75);
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(229, 231, 235, 0.6);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all 0.3s var(--ease-out-expo);
    font-family: var(--font-body);
    position: relative;
    overflow: hidden;
    animation: scaleIn 0.45s var(--ease-out-expo) both;
}

/* Staggered entrance for tool cards */
.tool-card:nth-child(1)  { animation-delay: 0.06s; }
.tool-card:nth-child(2)  { animation-delay: 0.09s; }
.tool-card:nth-child(3)  { animation-delay: 0.12s; }
.tool-card:nth-child(4)  { animation-delay: 0.15s; }
.tool-card:nth-child(5)  { animation-delay: 0.18s; }
.tool-card:nth-child(6)  { animation-delay: 0.21s; }
.tool-card:nth-child(7)  { animation-delay: 0.24s; }
.tool-card:nth-child(8)  { animation-delay: 0.27s; }
.tool-card:nth-child(9)  { animation-delay: 0.30s; }
.tool-card:nth-child(10) { animation-delay: 0.33s; }
.tool-card:nth-child(11) { animation-delay: 0.36s; }
.tool-card:nth-child(12) { animation-delay: 0.39s; }

.tool-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient);
    opacity: 0;
    transition: opacity 0.3s;
    border-radius: inherit;
    z-index: 0;
}

.tool-card:hover {
    border-color: transparent;
    box-shadow: var(--shadow-xl);
    transform: translateY(-6px);
}

.tool-card:hover::before {
    opacity: 0.06;
}

.tool-card:active {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.tool-card-icon {
    font-size: 36px;
    position: relative;
    z-index: 1;
    transition: transform 0.35s var(--ease-spring);
}

.tool-card:hover .tool-card-icon {
    transform: scale(1.2) translateY(-2px);
}

.tool-card-name {
    font-size: 13px;
    font-weight: 600;
    color: var(--gray-700);
    position: relative;
    z-index: 1;
    letter-spacing: -0.01em;
    transition: color 0.25s;
}

.tool-card:hover .tool-card-name {
    color: var(--primary);
}

/* ===== Tool View ===== */
.tool-view {
    max-width: 800px;
    margin: 0 auto;
    animation: fadeInUp 0.45s var(--ease-out-expo);
}

.tool-header {
    margin-bottom: 28px;
}

.tool-title {
    font-family: var(--font-heading);
    font-size: 26px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 6px;
    letter-spacing: -0.03em;
}

.tool-desc {
    font-size: 14.5px;
    color: var(--gray-500);
    line-height: 1.5;
}

/* ===== Error Message ===== */
.error-message {
    display: none;
    background: var(--red-50);
    border: 1px solid var(--red-100);
    color: var(--red-600);
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    margin-bottom: 16px;
    font-weight: 500;
}

.error-message.visible {
    display: block;
}

/* ===== Upload Zone ===== */
.upload-zone {
    border: 2px dashed var(--gray-300);
    border-radius: var(--radius-xl);
    padding: 48px 24px;
    text-align: center;
    cursor: pointer;
    transition: all 0.35s var(--ease-out-expo);
    background: rgba(255,255,255,0.6);
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
    margin-bottom: 20px;
    position: relative;
    animation: scaleIn 0.45s 0.1s var(--ease-out-expo) both;
}

.upload-zone:hover {
    border-color: var(--primary-light);
    background: rgba(37, 99, 235, 0.03);
    box-shadow: var(--shadow-glow);
    transform: scale(1.01);
}

.upload-zone.drag-over {
    border-color: var(--primary-light);
    background: rgba(37, 99, 235, 0.06);
    border-style: solid;
    box-shadow: 0 0 40px rgba(37, 99, 235, 0.18);
    transform: scale(1.02);
}

.upload-zone.has-file {
    border-style: solid;
    border-color: var(--green-500);
    background: var(--green-50);
}

.upload-icon {
    font-size: 44px;
    margin-bottom: 14px;
    display: block;
    animation: float 3s ease-in-out infinite;
}

.upload-text {
    font-size: 15px;
    color: var(--gray-600);
    margin-bottom: 16px;
}

.upload-text strong {
    color: var(--primary);
}

.upload-btn {
    display: inline-block;
    padding: 10px 28px;
    background: var(--gradient);
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    font-family: var(--font-body);
    transition: all 0.3s var(--ease-out-expo);
    letter-spacing: 0.01em;
}

.upload-btn:hover {
    background: var(--gradient-hover);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.35);
    transform: translateY(-2px);
}

.upload-btn:active {
    transform: translateY(0);
}

.upload-input {
    display: none;
}

/* ===== File Info ===== */
.file-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 16px;
}

.file-info {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-sm);
}

.file-info-icon {
    font-size: 20px;
    flex-shrink: 0;
}

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

.file-info-name {
    font-size: 14px;
    font-weight: 600;
    color: var(--gray-800);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-info-size {
    font-size: 12px;
    color: var(--gray-400);
}

.file-remove-btn {
    background: none;
    border: none;
    color: var(--gray-400);
    cursor: pointer;
    font-size: 18px;
    padding: 4px;
    line-height: 1;
    border-radius: 4px;
    transition: all 0.2s;
}

.file-remove-btn:hover {
    color: var(--red-500);
    background: var(--red-50);
}

/* ===== Options Panel ===== */
.options-panel {
    background: rgba(255,255,255,0.75);
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
    border: 1px solid rgba(229, 231, 235, 0.6);
    border-radius: var(--radius-lg);
    padding: 22px;
    margin-bottom: 18px;
    animation: fadeInUp 0.35s var(--ease-out-expo) both;
}

.options-panel h3 {
    font-family: var(--font-heading);
    font-size: 16px;
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 12px;
}

.options-panel label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-700);
    margin-bottom: 6px;
}

.options-panel input[type="text"],
.options-panel input[type="number"],
.options-panel input[type="password"],
.options-panel select,
.options-panel textarea {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-family: var(--font-body);
    color: var(--gray-800);
    background: var(--white);
    transition: border-color 0.2s;
    margin-bottom: 12px;
}

.options-panel input:focus,
.options-panel select:focus,
.options-panel textarea:focus {
    outline: none;
    border-color: var(--primary-light);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ===== Radio Option Groups ===== */
.radio-group {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 16px;
}

.radio-option {
    padding: 8px 16px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    color: var(--gray-600);
    background: var(--white);
    cursor: pointer;
    transition: all 0.2s;
    font-family: var(--font-body);
}

.radio-option:hover {
    border-color: var(--primary-light);
    color: var(--primary);
}

.radio-option.selected {
    background: linear-gradient(135deg, rgba(30,58,138,0.08), rgba(37,99,235,0.12));
    border-color: var(--primary-light);
    color: var(--primary);
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.12);
}

/* ===== Thumbnail Grid ===== */
.thumbnail-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 12px;
    margin-bottom: 16px;
}

.thumbnail-item {
    position: relative;
    background: var(--white);
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-sm);
    overflow: hidden;
    cursor: pointer;
    transition: all 0.2s;
    aspect-ratio: 3/4;
}

.thumbnail-item:hover {
    border-color: var(--primary-light);
    box-shadow: var(--shadow-sm);
}

.thumbnail-item.selected {
    border-color: var(--primary-light);
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.2);
}

.thumbnail-item canvas {
    width: 100%;
    height: 100%;
    object-fit: contain;
    display: block;
}

.thumbnail-label {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0,0,0,0.65);
    color: var(--white);
    font-size: 11px;
    font-weight: 600;
    text-align: center;
    padding: 3px;
}

.thumbnail-checkbox {
    position: absolute;
    top: 6px;
    right: 6px;
    width: 20px;
    height: 20px;
    border-radius: 4px;
    border: 2px solid var(--gray-300);
    background: var(--white);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    transition: all 0.2s;
}

.thumbnail-item.selected .thumbnail-checkbox {
    background: var(--primary-light);
    border-color: var(--primary-light);
    color: var(--white);
}

/* ===== Action Button ===== */
.action-area {
    margin-bottom: 16px;
}

.action-btn {
    width: 100%;
    padding: 16px 24px;
    background: var(--gradient);
    background-size: 200% 200%;
    color: var(--white);
    border: none;
    border-radius: var(--radius-md);
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    font-family: var(--font-heading);
    transition: all 0.3s var(--ease-out-expo);
    letter-spacing: 0.01em;
    position: relative;
    overflow: hidden;
}

.action-btn::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
    transform: translateX(-100%);
    transition: transform 0.5s;
}

.action-btn:hover::after {
    transform: translateX(100%);
}

.action-btn:hover {
    background: var(--gradient-hover);
    box-shadow: 0 8px 28px rgba(30, 58, 138, 0.3);
    transform: translateY(-2px);
}

.action-btn:active {
    transform: translateY(0);
    box-shadow: var(--shadow-md);
}

.action-btn:disabled {
    opacity: 0.45;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.action-btn:disabled::after {
    display: none;
}

/* ===== Progress Bar ===== */
.progress-area {
    display: none;
    margin-bottom: 16px;
}

.progress-area.visible {
    display: block;
}

.progress-bar-track {
    width: 100%;
    height: 8px;
    background: var(--gray-200);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 6px;
}

.progress-bar-fill {
    height: 100%;
    background: var(--gradient);
    border-radius: 4px;
    transition: width 0.3s ease;
    width: 0%;
    position: relative;
    overflow: hidden;
}

.progress-bar-fill::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.35), transparent);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}

.progress-text {
    font-size: 13px;
    color: var(--gray-500);
    text-align: center;
}

/* ===== Result Area ===== */
.result-area {
    display: none;
    background: var(--green-50);
    border: 1px solid var(--green-100);
    border-radius: var(--radius-md);
    padding: 20px;
    text-align: center;
    margin-bottom: 16px;
}

.result-area.visible {
    display: block;
    animation: scaleIn 0.4s var(--ease-spring);
}

.result-icon {
    font-size: 36px;
    margin-bottom: 8px;
    display: block;
}

.result-title {
    font-family: var(--font-heading);
    font-size: 18px;
    font-weight: 700;
    color: var(--green-700);
    margin-bottom: 4px;
}

.result-stats {
    font-size: 13px;
    color: var(--gray-500);
    margin-bottom: 16px;
}

.download-btn {
    display: inline-block;
    padding: 12px 32px;
    background: var(--green-600);
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-weight: 700;
    cursor: pointer;
    font-family: var(--font-heading);
    transition: all 0.2s;
    text-decoration: none;
}

.download-btn:hover {
    background: var(--green-700);
    box-shadow: 0 6px 20px rgba(22, 163, 74, 0.3);
    transform: translateY(-2px);
}

/* ===== Preview Area ===== */
.preview-area {
    margin-bottom: 16px;
}

/* ===== Signature Pad ===== */
.signature-pad-wrapper {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-md);
    overflow: hidden;
    margin-bottom: 16px;
}

.signature-pad {
    width: 100%;
    height: 200px;
    cursor: crosshair;
    display: block;
    touch-action: none;
}

.signature-actions {
    display: flex;
    gap: 8px;
    padding: 10px;
    border-top: 1px solid var(--gray-200);
}

.signature-actions button {
    padding: 6px 14px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-sm);
    background: var(--white);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    font-family: var(--font-body);
    color: var(--gray-600);
    transition: all 0.2s;
}

.signature-actions button:hover {
    border-color: var(--primary-light);
    color: var(--primary);
}

/* ===== Tab Bar ===== */
.tab-bar {
    display: flex;
    border-bottom: 2px solid var(--gray-200);
    margin-bottom: 16px;
}

.tab-item {
    padding: 10px 20px;
    border: none;
    background: none;
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-500);
    cursor: pointer;
    font-family: var(--font-body);
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.2s;
}

.tab-item:hover {
    color: var(--gray-700);
}

.tab-item.active {
    color: var(--primary);
    border-bottom-color: var(--primary-light);
    font-weight: 600;
}

/* ===== Privacy Footer ===== */
.privacy-footer {
    text-align: center;
    padding: 20px;
    font-size: 12px;
    color: var(--gray-400);
    border-top: 1px solid var(--gray-100);
    margin-top: 24px;
}

.privacy-footer strong {
    color: var(--gray-500);
}

/* ===== Mobile Responsive ===== */
@media (max-width: 768px) {
    .header-inner {
        padding: 0 16px;
    }

    .privacy-badge {
        display: none;
    }

    .hamburger {
        display: flex;
    }

    .sidebar {
        position: fixed;
        left: -100%;
        top: var(--header-height);
        z-index: 200;
        width: 260px;
        height: calc(100vh - var(--header-height));
        transition: left 0.3s ease;
        box-shadow: var(--shadow-lg);
    }

    .sidebar.open {
        left: 0;
    }

    .sidebar-overlay.visible {
        display: block;
    }

    .main-content {
        padding: 20px 16px;
    }

    .tool-grid {
        grid-template-columns: repeat(3, 1fr);
        gap: 12px;
    }

    .tool-card {
        padding: 16px 8px;
    }

    .tool-card-icon {
        font-size: 26px;
    }

    .tool-card-name {
        font-size: 12px;
    }

    .welcome-title {
        font-size: 22px;
    }

    .upload-zone {
        padding: 28px 16px;
    }

    .thumbnail-grid {
        grid-template-columns: repeat(auto-fill, minmax(90px, 1fr));
    }
}

@media (max-width: 480px) {
    .header-title {
        font-size: 18px;
    }

    .back-link {
        font-size: 13px;
    }

    .tool-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 10px;
    }

    .tool-card {
        padding: 14px 8px;
    }

    .tool-card-icon {
        font-size: 22px;
    }

    .tool-card-name {
        font-size: 11px;
    }

    .radio-group {
        flex-direction: column;
    }

    .radio-option {
        width: 100%;
        text-align: center;
    }
}

/* ===== Merge Module: Drag & Drop ===== */
.merge-drag-handle {
    cursor: grab;
    color: var(--gray-400);
    font-size: 16px;
    padding: 0 6px;
    -webkit-user-select: none;
    user-select: none;
    transition: color 0.2s;
}

.merge-drag-handle:hover {
    color: var(--gray-700);
}

.merge-file-item {
    transition: box-shadow 0.2s, background 0.2s, transform 0.2s;
}

.merge-file-item.drag-over {
    background: rgba(37, 99, 235, 0.06);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.15);
    transform: scale(1.01);
}

.merge-drag-fallback {
    opacity: 0.9;
    box-shadow: 0 8px 24px rgba(0,0,0,0.18) !important;
    background: white !important;
    border-radius: var(--radius-sm);
    z-index: 9999;
}

.merge-file-item.sortable-chosen {
    box-shadow: 0 4px 16px rgba(37, 99, 235, 0.2);
}

/* ===== Merge Module: Page Range Input ===== */
.merge-page-range {
    width: 80px;
    padding: 5px 8px;
    font-size: 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius-sm);
    font-family: var(--font-body);
    color: var(--gray-700);
    background: var(--white);
    flex-shrink: 0;
    transition: border-color 0.2s;
}

.merge-page-range:focus {
    outline: none;
    border-color: var(--primary-light);
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.1);
}

.merge-page-range::placeholder {
    color: var(--gray-400);
}

/* ===== PDF Editor Overlays ===== */
.edit-text-overlay { z-index: 10; }
.edit-text-overlay:hover { border-color: #93c5fd !important; background: rgba(37, 99, 235, 0.1) !important; }
.edit-mode-btn.active { background: #1e3a8a !important; color: white !important; border-color: #1e3a8a !important; }