/* CSS Variables for Premium Design System */
:root {
    --bg-dark: #0f1016;
    --bg-card: #181922;
    --bg-sidebar: #111219;
    --border-color: #242636;
    --text-primary: #f1f3f9;
    --text-secondary: #8b92b6;
    --accent-blue: #3b82f6;
    --accent-blue-hover: #2563eb;
    --accent-blue-alpha: rgba(59, 130, 246, 0.15);
    --accent-green: #10b981;
    --accent-green-alpha: rgba(16, 185, 129, 0.15);
    --accent-red: #ef4444;
    --accent-red-alpha: rgba(239, 68, 68, 0.15);
    --accent-yellow: #f59e0b;
    --accent-yellow-alpha: rgba(245, 158, 11, 0.15);
    --accent-orange: #f97316;
    --accent-orange-alpha: rgba(249, 115, 22, 0.15);
    --accent-purple: #8b5cf6;
    --accent-purple-alpha: rgba(139, 92, 246, 0.15);
    --transition-speed: 0.3s;
}

/* Reset and Global Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-primary);
    overflow-x: hidden;
    height: 100vh;
}

/* Layout Container */
.app-container {
    display: flex;
    height: 100vh;
    width: 100vw;
}

/* Sidebar Navigation */
.sidebar {
    width: 280px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 24px;
    flex-shrink: 0;
}

.logo-area {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 40px;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    color: #fff;
    font-size: 1.2rem;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.logo-text {
    font-size: 1.4rem;
    font-weight: 600;
    letter-spacing: 0.5px;
}

.logo-text span {
    color: var(--accent-blue);
    font-weight: 400;
}

.nav-menu {
    display: flex;
    flex-direction: column;
    gap: 8px;
    flex-grow: 1;
}

.nav-item {
    background: none;
    border: none;
    outline: none;
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 16px;
    border-radius: 12px;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    text-align: left;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
}

.nav-item:hover {
    background-color: rgba(255, 255, 255, 0.03);
    color: var(--text-primary);
}

.nav-item.active {
    background-color: var(--accent-blue-alpha);
    color: var(--accent-blue);
    box-shadow: inset 0 0 0 1px rgba(59, 130, 246, 0.2);
}

.nav-icon {
    font-size: 1.2rem;
}

.sidebar-footer {
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

/* Main Content Area */
.main-content {
    flex-grow: 1;
    overflow-y: auto;
    padding: 40px;
    display: flex;
    flex-direction: column;
    gap: 30px;
}

.main-header {
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 20px;
}

.main-header h1 {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 6px;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* Module Panels & Grid */
.module-panel {
    display: none;
    animation: fadeIn 0.4s ease-out forwards;
}

.module-panel.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.upload-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 24px;
    margin-bottom: 30px;
}

.upload-grid.triple {
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.upload-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 8px;
    transition: transform 0.2s ease, border-color 0.2s ease;
}

.upload-card:hover {
    border-color: rgba(59, 130, 246, 0.4);
}

.analysis-option {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    width: 100%;
    margin: 0 0 24px;
    padding: 16px 18px;
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    cursor: pointer;
}

.analysis-option:hover {
    border-color: rgba(59, 130, 246, 0.4);
    background-color: rgba(59, 130, 246, 0.05);
}

.analysis-option input {
    width: 18px;
    height: 18px;
    margin-top: 2px;
    accent-color: var(--accent-blue);
    flex-shrink: 0;
}

.analysis-option span {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.analysis-option strong {
    font-size: 0.95rem;
    font-weight: 600;
}

.analysis-option small {
    color: var(--text-secondary);
    font-size: 0.82rem;
    line-height: 1.4;
}

.upload-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
}

.upload-desc {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

/* Drag and Drop Zone */
.drop-zone {
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    padding: 30px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 12px;
    cursor: pointer;
    background-color: rgba(255, 255, 255, 0.01);
    transition: all var(--transition-speed) ease;
    text-align: center;
}

.drop-zone:hover, .drop-zone.dragover {
    border-color: var(--accent-blue);
    background-color: var(--accent-blue-alpha);
}

.drop-icon {
    font-size: 2rem;
    filter: drop-shadow(0 2px 8px rgba(59, 130, 246, 0.2));
}

.drop-text {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.file-name-display {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--accent-blue);
    background-color: rgba(59, 130, 246, 0.1);
    padding: 4px 10px;
    border-radius: 6px;
    max-width: 100%;
    word-break: break-all;
}

.file-input {
    display: none;
}

/* Buttons */
.action-bar {
    display: flex;
    justify-content: flex-end;
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    color: #fff;
    border: none;
    outline: none;
    font-family: inherit;
    font-size: 1rem;
    font-weight: 600;
    padding: 14px 32px;
    border-radius: 12px;
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(139, 92, 246, 0.3);
    transition: all 0.2s ease;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 25px rgba(139, 92, 246, 0.4);
}

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

.btn-primary.small {
    padding: 10px 18px;
    font-size: 0.88rem;
    margin-top: 12px;
}

.btn-secondary {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    outline: none;
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 500;
    padding: 10px 20px;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-secondary:hover {
    border-color: var(--accent-blue);
    background-color: rgba(255, 255, 255, 0.02);
}

.btn-export {
    background-color: var(--accent-blue-alpha);
    border: 1px solid rgba(59, 130, 246, 0.2);
    color: var(--accent-blue);
    padding: 8px 16px;
    border-radius: 8px;
    font-family: inherit;
    font-weight: 500;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

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

.btn-export.danger {
    background-color: var(--accent-red-alpha);
    border-color: rgba(239, 68, 68, 0.25);
    color: var(--accent-red);
}

.btn-export.danger:hover {
    background-color: var(--accent-red);
    color: #fff;
}

.workspace-panel {
    display: none;
    margin-top: 28px;
    flex-direction: column;
    gap: 20px;
}

.workspace-panel.active {
    display: flex;
}

.results-header-bar.compact {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 18px;
}

.action-feedback {
    display: none;
    border: 1px solid rgba(16, 185, 129, 0.28);
    border-radius: 14px;
    background-color: var(--accent-green-alpha);
    color: #b7f7dc;
    padding: 13px 16px;
    font-size: 0.9rem;
    font-weight: 600;
}

.action-feedback.active {
    display: block;
}

.tool-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 20px;
}

.tool-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.tool-card h3 {
    font-size: 1rem;
    font-weight: 600;
}

.wide-tool-card {
    grid-column: 1 / -1;
}

.tool-card-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 14px;
}

.hidden-control {
    display: none;
}

.column-picker {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
    gap: 10px;
    max-height: 260px;
    overflow: auto;
    padding: 4px;
}

.column-token {
    display: flex;
    align-items: center;
    gap: 10px;
    min-height: 46px;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    background-color: rgba(255, 255, 255, 0.025);
    color: var(--text-primary);
    padding: 9px 11px;
    font-family: inherit;
    cursor: pointer;
    text-align: left;
    transition: all 0.18s ease;
}

.column-token:hover {
    border-color: rgba(59, 130, 246, 0.55);
    background-color: rgba(59, 130, 246, 0.08);
}

.column-token.selected {
    border-color: var(--accent-blue);
    background-color: var(--accent-blue-alpha);
    box-shadow: inset 0 0 0 1px rgba(59, 130, 246, 0.15);
}

.column-token-index {
    width: 26px;
    height: 26px;
    border-radius: 8px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: rgba(255, 255, 255, 0.06);
    color: var(--text-secondary);
    font-size: 0.76rem;
    font-weight: 700;
    flex-shrink: 0;
}

.column-token.selected .column-token-index {
    background-color: var(--accent-blue);
    color: #fff;
}

.column-token-name {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    font-weight: 600;
    font-size: 0.88rem;
}

.operation-board {
    display: grid;
    grid-template-columns: 1.35fr 0.85fr 1fr;
    gap: 14px;
    align-items: stretch;
}

.operation-card {
    position: relative;
    display: flex;
    flex-direction: column;
    gap: 10px;
    border: 1px solid var(--border-color);
    border-radius: 14px;
    background-color: rgba(255, 255, 255, 0.02);
    padding: 16px;
}

.operation-card h4 {
    font-size: 0.95rem;
    font-weight: 700;
    padding-left: 36px;
}

.operation-preview {
    color: var(--text-secondary);
    font-size: 0.84rem;
    line-height: 1.45;
}

.primary-op {
    border-color: rgba(59, 130, 246, 0.25);
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.08), rgba(255, 255, 255, 0.02));
}

.danger-op {
    border-color: rgba(239, 68, 68, 0.18);
}

.step-pill {
    position: absolute;
    top: 13px;
    left: 14px;
    width: 26px;
    height: 26px;
    border-radius: 999px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: var(--accent-blue-alpha);
    color: var(--accent-blue);
    font-size: 0.8rem;
    font-weight: 800;
}

.cleanup-strip {
    display: flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    border-top: 1px solid var(--border-color);
    padding-top: 14px;
}

.cleanup-strip span {
    color: var(--text-secondary);
    font-size: 0.84rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.4px;
}

.btn-export.muted {
    background-color: rgba(255, 255, 255, 0.04);
    border-color: var(--border-color);
    color: var(--text-secondary);
}

.form-control {
    width: 100%;
    min-height: 40px;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    background-color: #111219;
    color: var(--text-primary);
    padding: 9px 12px;
    font-family: inherit;
    outline: none;
}

.form-control:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.12);
}

select.form-control[multiple] {
    min-height: 140px;
}

.form-control.short {
    max-width: 120px;
}

.inline-fields {
    display: flex;
    gap: 10px;
    align-items: center;
}

.button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.detail-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
    max-height: 460px;
    overflow: auto;
}

.detail-card {
    border: 1px solid var(--border-color);
    border-radius: 12px;
    background-color: rgba(255, 255, 255, 0.02);
    padding: 12px;
}

.detail-card summary {
    cursor: pointer;
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: 10px;
}

.detail-card label {
    display: block;
    color: var(--text-secondary);
    font-size: 0.82rem;
    margin: 10px 0 6px;
}

.mini-rows {
    display: flex;
    flex-direction: column;
    gap: 8px;
    color: var(--text-secondary);
    font-size: 0.8rem;
    line-height: 1.4;
}

.pair-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.compact-kpis {
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
}

.spaced {
    margin-top: 12px;
}

.section-heading-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    margin-top: 10px;
}

.section-heading-row h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 4px;
}

.value-chip-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
    gap: 8px;
    max-height: 190px;
    overflow: auto;
    padding-right: 4px;
}

.value-chip {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    background-color: rgba(255, 255, 255, 0.025);
    color: var(--text-primary);
    padding: 9px 10px;
    font-family: inherit;
    cursor: pointer;
    text-align: left;
}

.value-chip:hover {
    border-color: var(--accent-blue);
    background-color: var(--accent-blue-alpha);
}

.value-chip span {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.value-chip strong {
    min-width: 28px;
    border-radius: 999px;
    background-color: rgba(255, 255, 255, 0.08);
    color: var(--accent-blue);
    padding: 2px 8px;
    text-align: center;
    font-size: 0.78rem;
}

.replace-panel {
    border-top: 1px solid var(--border-color);
    margin-top: 4px;
    padding-top: 14px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.replace-panel h4 {
    font-size: 0.95rem;
    font-weight: 600;
}

.duplicates-board {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.duplicate-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 14px;
    overflow: hidden;
}

.duplicate-card summary {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 14px;
    padding: 14px 16px;
    cursor: pointer;
    font-weight: 600;
}

.duplicate-card summary span {
    color: var(--text-primary);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.duplicate-card summary strong {
    color: var(--accent-yellow);
    background-color: var(--accent-yellow-alpha);
    border: 1px solid rgba(245, 158, 11, 0.18);
    border-radius: 999px;
    padding: 4px 10px;
    font-size: 0.82rem;
    white-space: nowrap;
}

.mini-table-scroll {
    overflow: auto;
    border-top: 1px solid var(--border-color);
}

.mini-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.8rem;
}

.mini-table th,
.mini-table td {
    padding: 10px 12px;
    border-bottom: 1px solid var(--border-color);
    white-space: nowrap;
    text-align: left;
}

.mini-table th {
    color: var(--text-primary);
    background-color: #1c1d27;
    font-weight: 600;
}

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

.empty-inline {
    border: 1px dashed var(--border-color);
    border-radius: 14px;
    color: var(--text-secondary);
    padding: 22px;
    text-align: center;
}

/* Spinner */
.spinner-container {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 20px;
    padding: 40px 0;
    animation: fadeIn 0.3s ease-in-out;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 3px solid rgba(255, 255, 255, 0.05);
    border-top: 3px solid var(--accent-blue);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Results Section */
.results-container {
    display: none;
    flex-direction: column;
    gap: 30px;
    animation: fadeIn 0.4s ease-out forwards;
}

.results-container.active {
    display: flex;
}

.results-header-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 16px;
}

.results-header-bar h2 {
    font-size: 1.4rem;
    font-weight: 600;
}

/* KPIs Dashboard */
.kpi-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 20px;
}

.kpi-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.kpi-title {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.kpi-val {
    font-size: 2.2rem;
    font-weight: 700;
    line-height: 1;
    margin: 4px 0;
}

.kpi-sub {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.text-green { color: var(--accent-green); }
.text-yellow { color: var(--accent-yellow); }
.text-red { color: var(--accent-red); }
.text-orange { color: var(--accent-orange); }
.text-purple { color: var(--accent-purple); }

/* Tabs Layout */
.tabs-container {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.tabs-header {
    display: flex;
    background-color: rgba(0, 0, 0, 0.2);
    border-bottom: 1px solid var(--border-color);
}

.tab-btn {
    background: none;
    border: none;
    outline: none;
    color: var(--text-secondary);
    padding: 18px 24px;
    font-family: inherit;
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    border-bottom: 2px solid transparent;
}

.tab-btn:hover {
    color: var(--text-primary);
}

.tab-btn.active {
    color: var(--accent-blue);
    border-bottom-color: var(--accent-blue);
    background-color: rgba(255, 255, 255, 0.01);
}

.tab-content {
    display: none;
    padding: 24px;
    animation: fadeIn 0.3s ease-out;
}

.tab-content.active {
    display: block;
}

/* Sub-tabs for Alerts */
.subtabs-header {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.subtab-btn {
    background-color: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-secondary);
    padding: 8px 16px;
    font-family: inherit;
    font-weight: 500;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.subtab-btn:hover {
    color: var(--text-primary);
    border-color: rgba(255, 255, 255, 0.15);
}

.subtab-btn.active {
    background-color: var(--accent-blue-alpha);
    border-color: var(--accent-blue);
    color: var(--accent-blue);
}

.alert-explainer {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    margin-bottom: 16px;
    padding: 16px;
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: 14px;
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.1), rgba(255, 255, 255, 0.02));
}

.alert-explainer-icon {
    width: 32px;
    height: 32px;
    border-radius: 10px;
    background-color: var(--accent-blue-alpha);
    color: var(--accent-blue);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    flex-shrink: 0;
}

.alert-explainer h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 4px;
}

.alert-explainer p {
    color: var(--text-secondary);
    font-size: 0.88rem;
    line-height: 1.5;
}

.tab-actions {
    display: flex;
    justify-content: flex-end;
    margin-bottom: 16px;
}

.raw-info {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
}

/* Premium Interactive Tables */
.table-scroll-container {
    overflow-x: auto;
    max-height: 500px;
    overflow-y: auto;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    position: relative;
}

.premium-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    text-align: left;
}

.premium-table th {
    background-color: #1c1d27;
    color: var(--text-primary);
    font-weight: 600;
    padding: 14px 16px;
    position: sticky;
    top: 0;
    z-index: 10;
    border-bottom: 2px solid var(--border-color);
    white-space: nowrap;
}

.premium-table td {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    white-space: nowrap;
}

.premium-table tr:hover td {
    background-color: rgba(255, 255, 255, 0.02);
    color: var(--text-primary);
}

/* Row-specific alert highlights */
.premium-table tr.alert-missing td {
    border-left: 3px solid var(--accent-yellow);
}

.premium-table tr.alert-extra td {
    border-left: 3px solid var(--accent-red);
}

.premium-table tr.alert-inconsistency td {
    border-left: 3px solid var(--accent-orange);
}

.premium-table tr.compare-ok td {
    border-left: 3px solid var(--accent-green);
}

.premium-table tr.compare-diff td {
    border-left: 3px solid var(--accent-yellow);
}

.premium-table tr.compare-missing td {
    border-left: 3px solid var(--accent-red);
}

/* Empty States */
.empty-state {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 20px;
    text-align: center;
    color: var(--text-secondary);
}

.empty-state span {
    font-size: 3rem;
    margin-bottom: 12px;
}

.empty-state p {
    font-size: 0.95rem;
}

@media (max-width: 860px) {
    body {
        height: auto;
    }

    .app-container {
        flex-direction: column;
        height: auto;
        min-height: 100vh;
    }

    .sidebar {
        width: 100%;
        padding: 18px;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
    }

    .logo-area {
        margin-bottom: 18px;
    }

    .nav-menu {
        flex-direction: row;
    }

    .nav-item {
        flex: 1;
        justify-content: center;
    }

    .sidebar-footer {
        display: none;
    }

    .main-content {
        padding: 24px 16px;
    }

    .results-header-bar,
    .tabs-header {
        align-items: stretch;
        flex-direction: column;
    }

    .operation-board {
        grid-template-columns: 1fr;
    }

    .tool-card-header {
        flex-direction: column;
    }

    .tab-btn {
        text-align: left;
    }
}

@media (max-width: 520px) {
    .main-header h1 {
        font-size: 1.45rem;
    }

    .upload-grid,
    .upload-grid.triple {
        grid-template-columns: 1fr;
    }

    .action-bar {
        justify-content: stretch;
    }

    .btn-primary,
    .btn-secondary {
        width: 100%;
        justify-content: center;
    }

    .alert-explainer {
        flex-direction: column;
    }

    .inline-fields {
        flex-direction: column;
        align-items: stretch;
    }

    .form-control.short {
        max-width: none;
    }
}