/* ============================================
   CSS Variables & Reset
   ============================================ */
:root {
    /* Dark Theme Colors */
    --color-primary: #3b82f6;
    --color-primary-hover: #2563eb;
    --color-primary-glow: rgba(59, 130, 246, 0.2);
    --color-secondary: #64748b;
    --color-danger: #ef4444;
    --color-danger-hover: #dc2626;
    --color-success: #10b981;
    --color-warning: #f59e0b;
    
    /* Dark Neutrals */
    --color-bg: #0f172a;
    --color-bg-alt: #1e293b;
    --color-bg-elevated: #334155;
    --color-border: #475569;
    --color-border-light: #334155;
    --color-text: #f1f5f9;
    --color-text-muted: #94a3b8;
    --color-text-dim: #64748b;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'SF Mono', Monaco, 'Cascadia Code', monospace;
    
    /* Layout */
    --header-height: 60px;
    --sidebar-width: 200px;
    --border-radius: 8px;
    --border-radius-sm: 4px;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
}

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

html {
    font-size: 14px;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.5;
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow: hidden;
}

button {
    font-family: inherit;
    font-size: inherit;
    cursor: pointer;
    border: none;
    outline: none;
}

input, select {
    font-family: inherit;
    font-size: inherit;
}

/* ============================================
   Header
   ============================================ */
.app-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background-color: var(--color-bg-alt);
    border-bottom: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--space-lg);
    z-index: 100;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    min-width: 0;
}

.header-brand {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.header-title-row {
    display: flex;
    align-items: center;
    gap: 10px;
}

.header-logo {
    height: 40px;
    width: auto;
}

@media (max-width: 768px) {
    .header-logo {
        display: none;
    }
}

.app-header h1 {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--color-text);
    white-space: nowrap;
    line-height: 1.2;
}

.header-tagline {
    font-size: 0.7rem;
    color: var(--color-text-muted);
    white-space: nowrap;
}

@media (max-width: 900px) {
    .header-tagline {
        display: none;
    }
}

.privacy-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
    padding: var(--space-xs) var(--space-sm);
    background-color: rgba(16, 185, 129, 0.1);
    border: 1px solid rgba(16, 185, 129, 0.3);
    border-radius: var(--border-radius-sm);
    font-size: 0.75rem;
    color: var(--color-success);
    cursor: help;
    white-space: nowrap;
}

.header-actions {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
    justify-content: flex-end;
}

/* Mobile menu toggle */
.menu-toggle {
    display: none;
    padding: var(--space-sm);
    background: var(--color-bg-elevated);
    border-radius: var(--border-radius-sm);
    color: var(--color-text);
    font-size: 1.25rem;
}

/* ============================================
   Buttons
   ============================================ */
button {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--border-radius-sm);
    font-weight: 500;
    transition: all 0.15s ease;
    white-space: nowrap;
    font-size: 0.85rem;
}

.btn-primary {
    background-color: var(--color-primary);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--color-primary-hover);
    box-shadow: 0 0 0 3px var(--color-primary-glow);
}

.btn-secondary {
    background-color: var(--color-bg-elevated);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
    background-color: var(--color-border);
    border-color: var(--color-text-muted);
}

.btn-danger {
    background-color: var(--color-danger);
    color: white;
}

.btn-danger:hover:not(:disabled) {
    background-color: var(--color-danger-hover);
}

button:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

button:active:not(:disabled) {
    transform: translateY(1px);
}

/* ============================================
   Layout
   ============================================ */
.app-container {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    display: flex;
    overflow: hidden;
}

.module-rail {
    width: var(--sidebar-width);
    background-color: var(--color-bg-alt);
    border-right: 1px solid var(--color-border);
    padding: var(--space-lg);
    overflow-y: auto;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
}

.module-rail h2 {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: var(--space-md);
}

.module-nav {
    display: flex;
    flex-direction: column;
    gap: var(--space-xs);
}

.module-nav button {
    width: 100%;
    text-align: left;
    padding: var(--space-sm) var(--space-md);
    background-color: transparent;
    color: var(--color-text-muted);
    border: 1px solid transparent;
    border-radius: var(--border-radius-sm);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.85rem;
    transition: all 0.15s ease;
}

.module-nav button:before {
    content: '○';
    font-size: 0.75rem;
    color: var(--color-text-dim);
}

.module-nav button.active:before {
    content: '●';
    color: var(--color-primary);
}

.module-nav button:hover {
    background-color: var(--color-bg-elevated);
    color: var(--color-text);
}

.module-nav button.active {
    background-color: var(--color-primary-glow);
    border-color: var(--color-primary);
    color: var(--color-primary);
    font-weight: 500;
}

.sidebar-footer {
    margin-top: auto;
    padding: var(--space-md);
    text-align: center;
    font-size: 0.8rem;
    color: var(--color-text-muted);
    line-height: 1.6;
    border-top: 1px solid var(--color-border-light);
}

.sidebar-footer span {
    display: block;
    margin-bottom: 4px;
}

.sidebar-footer a {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.15s ease;
}

.sidebar-footer a:hover {
    color: var(--color-primary-hover);
    text-decoration: underline;
}

.content-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    min-width: 0;
}

/* ============================================
   Panels
   ============================================ */
.data-panel,
.results-panel {
    display: flex;
    flex-direction: column;
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
}

.data-panel {
    flex: 1;
    min-height: 0;
}

.results-panel {
    flex: 1;
    min-height: 0;
}

.panel-header {
    padding: var(--space-sm) var(--space-lg);
    border-bottom: 1px solid var(--color-border);
    background-color: var(--color-bg-alt);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
    flex-wrap: wrap;
    min-height: 50px;
}

.panel-header h2 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-text);
}

/* ============================================
   Sheet Tabs
   ============================================ */
.sheet-tabs {
    display: flex;
    gap: var(--space-xs);
}

.sheet-tabs .tab {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 2px;
    padding: var(--space-sm) var(--space-md);
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    color: var(--color-text-muted);
    transition: all 0.15s ease;
}

.sheet-tabs .tab:hover {
    border-color: var(--color-text-muted);
    color: var(--color-text);
}

.sheet-tabs .tab.active {
    background-color: var(--color-primary);
    border-color: var(--color-primary);
    color: white;
}

.tab-label {
    font-weight: 500;
    font-size: 0.8rem;
}

.tab-badge {
    font-size: 0.65rem;
    opacity: 0.8;
}

/* ============================================
   Controls
   ============================================ */
.sheet-controls,
.results-actions {
    display: flex;
    gap: var(--space-sm);
    align-items: center;
    flex-wrap: wrap;
}

.control-label {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.8rem;
    color: var(--color-text-muted);
    font-weight: 500;
}

.select-input {
    padding: var(--space-xs) var(--space-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    background-color: var(--color-bg);
    color: var(--color-text);
    min-width: 120px;
    font-size: 0.85rem;
}

.select-input:focus {
    outline: none;
    border-color: var(--color-primary);
}

.search-input {
    padding: var(--space-xs) var(--space-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    background-color: var(--color-bg);
    color: var(--color-text);
    width: 180px;
    font-size: 0.85rem;
}

.search-input::placeholder {
    color: var(--color-text-dim);
}

.search-input:focus {
    outline: none;
    border-color: var(--color-primary);
}

/* ============================================
   Empty States
   ============================================ */
.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    padding: var(--space-xl);
    text-align: center;
    color: var(--color-text-muted);
}

.empty-icon {
    font-size: 3rem;
    margin-bottom: var(--space-md);
    opacity: 0.5;
}

.empty-state h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--space-sm);
}

.empty-state p {
    font-size: 0.9rem;
    margin-bottom: var(--space-lg);
    max-width: 300px;
}

.empty-hero {
    margin-bottom: var(--space-xl);
}

.empty-hero h2 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--space-sm);
}

.empty-subtitle {
    font-size: 1rem;
    color: var(--color-text-muted);
}

.task-cards {
    display: flex;
    gap: var(--space-md);
    flex-wrap: wrap;
    justify-content: center;
    max-width: 920px;
    margin-bottom: var(--space-xl);
}

@media (max-width: 768px) {
    .task-cards {
        flex-direction: column;
        align-items: center;
        gap: var(--space-sm);
        margin-bottom: var(--space-md);
    }
    
    .task-card {
        width: 100%;
        max-width: 320px;
        min-height: auto;
        padding: var(--space-md);
    }
    
    .task-card-icon {
        font-size: 1.25rem;
    }
    
    .task-card-content h3 {
        font-size: 0.8rem;
    }
    
    .task-card-content p {
        font-size: 0.7rem;
        line-height: 1.3;
    }
    
    .task-card-badge {
        font-size: 0.5rem;
        padding: 3px 8px;
        top: -8px;
    }
    
    .empty-hero {
        margin-bottom: var(--space-md);
    }
    
    .empty-hero h2 {
        font-size: 1.2rem;
    }
    
    .empty-subtitle {
        font-size: 0.85rem;
    }
}

.task-card {
    display: flex;
    align-items: flex-start;
    gap: var(--space-md);
    padding: var(--space-lg);
    background: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    cursor: pointer;
    text-align: left;
    transition: all 0.2s ease;
    width: 280px;
    min-height: 90px;
    position: relative;
    box-sizing: border-box;
}

.task-card:hover {
    border-color: var(--color-primary);
    background: var(--color-bg-elevated);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.task-card-featured {
    border-color: var(--color-primary);
    background: rgba(37, 99, 235, 0.05);
}

.task-card-featured:hover {
    background: rgba(37, 99, 235, 0.1);
}

.task-card-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
    width: 32px;
    text-align: center;
}

.task-card-content {
    flex: 1;
    min-width: 0;
    word-wrap: break-word;
    overflow-wrap: break-word;
}

.task-card-content h3 {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 6px;
    word-wrap: break-word;
}

.task-card-content p {
    font-size: 0.75rem;
    color: var(--color-text-muted);
    line-height: 1.4;
    margin: 0;
    word-wrap: break-word;
}

.task-card-badge {
    position: absolute;
    top: -10px;
    right: var(--space-md);
    background: linear-gradient(135deg, #f59e0b 0%, #f97316 100%);
    color: white;
    font-size: 0.6rem;
    font-weight: 700;
    padding: 4px 10px;
    border-radius: 12px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    box-shadow: 0 2px 8px rgba(245, 158, 11, 0.4);
}

.empty-divider {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    width: 100%;
    max-width: 400px;
    margin-bottom: var(--space-lg);
    color: var(--color-text-dim);
    font-size: 0.8rem;
}

.empty-divider::before,
.empty-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--color-border);
}

.empty-actions {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    flex-wrap: wrap;
    justify-content: center;
}

.empty-or {
    color: var(--color-text-dim);
    font-size: 0.85rem;
}

/* ============================================
   Metrics Strip
   ============================================ */
.metrics-strip {
    display: flex;
    gap: var(--space-lg);
    padding: var(--space-md) var(--space-lg);
    background-color: var(--color-bg-alt);
    border-bottom: 1px solid var(--color-border);
    flex-wrap: wrap;
    min-height: 60px;
}

.metric {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.metric-label {
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-dim);
}

.metric-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-text);
}

.metric-value.success {
    color: var(--color-success);
}

.metric-value.warning {
    color: var(--color-warning);
}

.metric-value.danger {
    color: var(--color-danger);
}

/* Clickable/Filterable Metrics */
.metric-filterable {
    cursor: pointer;
    padding: var(--space-sm);
    margin: calc(var(--space-sm) * -1);
    border-radius: var(--border-radius-sm);
    transition: background-color 0.15s ease, transform 0.1s ease;
}

.metric-filterable:hover {
    background-color: var(--color-bg-elevated);
}

.metric-filterable:active {
    transform: scale(0.98);
}

.metric-filterable .metric-value.clickable {
    text-decoration: underline;
    text-decoration-style: dotted;
    text-underline-offset: 3px;
}

.metric-filterable.metric-active {
    background-color: var(--color-bg-elevated);
    box-shadow: inset 0 0 0 2px var(--color-primary);
}

.metric-filterable.metric-active .metric-label::after {
    content: ' ✓';
    color: var(--color-primary);
}

/* ============================================
   Filter Explanation Banner
   ============================================ */
.filter-banner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
    padding: var(--space-sm) var(--space-lg);
    background: linear-gradient(135deg, rgba(239, 68, 68, 0.15) 0%, rgba(239, 68, 68, 0.08) 100%);
    border-left: 4px solid var(--color-danger);
    border-bottom: 1px solid rgba(239, 68, 68, 0.3);
    animation: banner-slide-in 0.3s ease-out;
}

.filter-banner.hidden {
    display: none;
}

.filter-banner.warning {
    background: linear-gradient(135deg, rgba(245, 158, 11, 0.15) 0%, rgba(245, 158, 11, 0.08) 100%);
    border-left-color: var(--color-warning);
    border-bottom-color: rgba(245, 158, 11, 0.3);
}

.filter-banner.info {
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.15) 0%, rgba(59, 130, 246, 0.08) 100%);
    border-left-color: var(--color-primary);
    border-bottom-color: rgba(59, 130, 246, 0.3);
}

.filter-banner-content {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.filter-banner-icon {
    font-size: 1.25rem;
}

.filter-banner-text {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.filter-banner-text strong {
    font-size: 0.875rem;
    color: var(--color-text);
}

.filter-banner-text span {
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.filter-banner-close {
    padding: var(--space-xs) var(--space-sm);
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--border-radius-sm);
    color: var(--color-text-muted);
    font-size: 0.75rem;
    cursor: pointer;
    transition: all 0.15s ease;
    white-space: nowrap;
}

.filter-banner-close:hover {
    background: rgba(255, 255, 255, 0.15);
    color: var(--color-text);
}

@keyframes banner-slide-in {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================================
   Modal
   ============================================ */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-md);
}

.modal.hidden {
    display: none;
}

.modal-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
}

.modal-content {
    position: relative;
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 600px;
    max-height: 80vh;
    display: flex;
    flex-direction: column;
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-lg);
    border-bottom: 1px solid var(--color-border);
}

.modal-header h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--color-text);
}

.modal-close {
    padding: var(--space-xs) var(--space-sm);
    font-size: 1.5rem;
    line-height: 1;
    color: var(--color-text-muted);
    background: none;
    border: none;
}

.modal-close:hover {
    color: var(--color-text);
}

.modal-body {
    padding: var(--space-lg);
    overflow-y: auto;
    flex: 1;
}

.modal-footer {
    padding: var(--space-lg);
    border-top: 1px solid var(--color-border);
    display: flex;
    justify-content: flex-end;
    gap: var(--space-sm);
}

.modal-large {
    max-width: 800px;
    max-height: 85vh;
}

/* ============================================
   Report Styles
   ============================================ */
.report-section {
    margin-bottom: var(--space-xl);
}

.report-section:last-child {
    margin-bottom: 0;
}

.report-section h4 {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--space-md);
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--color-border);
}

.report-summary {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
}

.report-stat {
    background: var(--color-bg);
    padding: var(--space-md);
    border-radius: var(--border-radius-sm);
    text-align: center;
}

.report-stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-text);
}

.report-stat-value.positive {
    color: var(--color-success);
}

.report-stat-value.negative {
    color: var(--color-danger);
}

.report-stat-label {
    font-size: 0.7rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-top: 4px;
}

.report-table {
    width: 100%;
    font-size: 0.85rem;
    border-collapse: collapse;
}

.report-table th,
.report-table td {
    padding: var(--space-sm) var(--space-md);
    text-align: left;
    border-bottom: 1px solid var(--color-border-light);
}

.report-table th {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    background: var(--color-bg);
}

.report-table td {
    color: var(--color-text);
}

.report-table .number {
    text-align: right;
    font-family: var(--font-mono);
}

.report-table .positive {
    color: var(--color-success);
}

.report-table .negative {
    color: var(--color-danger);
}

.report-table .total-row {
    font-weight: 600;
    background: var(--color-bg);
}

.report-table .total-row td {
    border-top: 2px solid var(--color-border);
}

.report-narrative {
    background: var(--color-bg);
    padding: var(--space-md);
    border-radius: var(--border-radius-sm);
    border-left: 3px solid var(--color-primary);
    font-size: 0.9rem;
    line-height: 1.6;
    color: var(--color-text-muted);
}

.report-narrative strong {
    color: var(--color-text);
}

.report-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.report-list li {
    padding: var(--space-sm) 0;
    border-bottom: 1px solid var(--color-border-light);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.report-list li:last-child {
    border-bottom: none;
}

.report-list .item-name {
    color: var(--color-text);
}

.report-list .item-detail {
    color: var(--color-text-muted);
    font-size: 0.8rem;
}

.report-list .item-value {
    font-family: var(--font-mono);
    font-weight: 600;
}

/* ============================================
   Sample Data Dropdown
   ============================================ */
.sample-dropdown {
    position: relative;
}

/* Inline dropdown (in empty state) - opens upward */
.sample-dropdown.inline-dropdown .sample-menu {
    bottom: 100%;
    top: auto;
    margin-bottom: 4px;
    margin-top: 0;
}

.sample-menu {
    position: absolute;
    top: 100%;
    left: 0;
    margin-top: 4px;
    background: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    min-width: 260px;
    z-index: 200;
    box-shadow: var(--shadow-lg);
    display: none;
    overflow: hidden;
}

.sample-menu.show {
    display: block;
}

.sample-menu-header {
    padding: var(--space-sm) var(--space-md);
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--color-text-dim);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
}

.sample-menu button {
    display: block;
    width: 100%;
    text-align: left;
    padding: var(--space-sm) var(--space-md);
    background: none;
    border: none;
    color: var(--color-text);
    font-size: 0.85rem;
    cursor: pointer;
    transition: background 0.15s;
}

.sample-menu button:hover {
    background: var(--color-bg-elevated);
}

.sample-menu button:not(:last-child) {
    border-bottom: 1px solid var(--color-border-light);
}

/* ============================================
   Toast Notifications
   ============================================ */
.toast {
    position: fixed;
    bottom: var(--space-xl);
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--color-success);
    color: white;
    padding: var(--space-sm) var(--space-lg);
    border-radius: var(--border-radius);
    font-size: 0.9rem;
    font-weight: 500;
    z-index: 2000;
    animation: toastIn 0.3s ease;
}

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

@keyframes toastIn {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}

/* ============================================
   Responsive - Tablet
   ============================================ */
@media (max-width: 1024px) {
    .header-actions .btn-secondary:not(#importCSV):not(#reset) {
        display: none;
    }
    
    .search-input {
        width: 140px;
    }
    
    .select-input {
        min-width: 100px;
    }
}

/* ============================================
   Responsive - Mobile
   ============================================ */
@media (max-width: 768px) {
    :root {
        --header-height: 56px;
        --sidebar-width: 100%;
    }
    
    html {
        font-size: 13px;
    }
    
    .app-header {
        padding: 0 var(--space-md);
    }
    
    .app-header h1 {
        font-size: 1rem;
    }
    
    .privacy-badge {
        display: none;
    }
    
    .header-actions {
        gap: var(--space-xs);
    }
    
    .header-actions button {
        padding: var(--space-xs) var(--space-sm);
        font-size: 0.8rem;
    }
    
    .header-actions .btn-secondary {
        display: none;
    }
    
    .header-actions #importCSV,
    .header-actions #reset {
        display: inline-flex;
    }
    
    .menu-toggle {
        display: flex;
    }
    
    /* Sidebar as overlay */
    .module-rail {
        position: fixed;
        left: 0;
        top: var(--header-height);
        bottom: 0;
        width: 260px;
        z-index: 50;
        transform: translateX(-100%);
        transition: transform 0.3s ease;
        box-shadow: var(--shadow-lg);
    }
    
    .module-rail.open {
        transform: translateX(0);
    }
    
    .module-rail-overlay {
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        bottom: 0;
        background: rgba(0, 0, 0, 0.5);
        z-index: 49;
        display: none;
    }
    
    .module-rail-overlay.show {
        display: block;
    }
    
    /* Stack panels vertically */
    .content-area {
        flex-direction: column;
    }
    
    .data-panel,
    .results-panel {
        flex: none;
        height: 50%;
    }
    
    .panel-header {
        padding: var(--space-sm) var(--space-md);
        gap: var(--space-sm);
    }
    
    .sheet-tabs .tab {
        padding: var(--space-xs) var(--space-sm);
    }
    
    .tab-label {
        font-size: 0.75rem;
    }
    
    .tab-badge {
        display: none;
    }
    
    .sheet-controls {
        width: 100%;
        justify-content: space-between;
    }
    
    .control-label {
        font-size: 0.75rem;
    }
    
    .select-input,
    .search-input {
        flex: 1;
        min-width: 0;
        font-size: 16px; /* Prevent iOS zoom */
    }
    
    .metrics-strip {
        padding: var(--space-sm) var(--space-md);
        gap: var(--space-md);
    }
    
    .metric-label {
        font-size: 0.6rem;
    }
    
    .metric-value {
        font-size: 1rem;
    }
    
    .results-actions {
        width: 100%;
    }
    
    .results-actions button {
        flex: 1;
        justify-content: center;
    }
    
    .empty-icon {
        font-size: 2.5rem;
    }
    
    .empty-state h3 {
        font-size: 1rem;
    }
    
    .empty-state p {
        font-size: 0.85rem;
    }
}

/* ============================================
   Responsive - Small Mobile
   ============================================ */
@media (max-width: 480px) {
    .header-actions button span {
        display: none;
    }
    
    .header-actions #importCSV:after {
        content: '📁';
    }
    
    .header-actions #reset:after {
        content: '🗑️';
    }
    
    .sheet-tabs {
        flex: 1;
    }
    
    .sheet-tabs .tab {
        flex: 1;
        justify-content: center;
        align-items: center;
    }
    
    .panel-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .sheet-controls {
        flex-direction: column;
    }
}

/* ============================================
   Utility Classes
   ============================================ */
.hidden {
    display: none !important;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}