/* ============================================================
    CSS Custom Properties
    ============================================================ */
    :root {
    --bg:            #f8fafc;
    --surface:       #ffffff;
    --border:        #e2e8f0;
    --text:          #1e293b;
    --text-secondary:#64748b;
    --text-muted:    #94a3b8;
    --accent:        #3b82f6;
    --accent-hover:  #2563eb;
    --accent-light:  #eff6ff;
    --danger:        #ef4444;
    --danger-hover:  #dc2626;
    --success:       #22c55e;
    --warning:       #f59e0b;
    --radius:        10px;
    --radius-sm:     6px;
    --shadow:        0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
    --shadow-lg:     0 4px 16px rgba(0,0,0,.08), 0 2px 6px rgba(0,0,0,.04);
    --font:          -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-mono:     "SF Mono", "Fira Code", "Fira Mono", monospace;
    --topbar-h:      52px;
    --panel-w:       340px;
    --transition:    150ms ease;
    }

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

    html, body {
    height: 100%; width: 100%;
    font-family: var(--font);
    font-size: 14px;
    color: var(--text);
    background: var(--bg);
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    }

    button {
    font-family: var(--font);
    cursor: pointer;
    border: none;
    background: none;
    font-size: inherit;
    }

    input, select {
    font-family: var(--font);
    font-size: 13px;
    }

    /* ============================================================
    App Layout (CSS Grid)
    ============================================================ */
    #app {
    display: grid;
    grid-template-rows: var(--topbar-h) 1fr;
    grid-template-columns: 1fr;
    height: 100vh;
    width: 100vw;
    }

    /* ---- Top Bar ---- */
    #topbar {
    grid-row: 1;
    grid-column: 1;
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 0 16px;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    /* Above the welcome overlay (50) so toolbar controls (e.g. the View
       popover) stay clickable before data loads; still below modals (100). */
    z-index: 60;
    }

    #topbar .logo {
    font-weight: 700;
    font-size: 15px;
    letter-spacing: -.01em;
    margin-right: 8px;
    white-space: nowrap;
    }

    #topbar .spacer { flex: 1; }

    /* Cluster related controls; dividers separate groups. */
    .topbar-group {
    display: flex;
    align-items: center;
    gap: 6px;
    }

    .topbar-divider {
    width: 1px;
    height: 22px;
    background: var(--border);
    flex: none;
    }

    /* ---- View popover ---- */
    .popover-wrap { position: relative; }

    .chevron {
    font-size: 10px;
    margin-left: 2px;
    transition: transform var(--transition);
    }

    [aria-expanded="true"] .chevron { transform: rotate(180deg); }

    .popover {
    position: absolute;
    top: calc(100% + 8px);
    left: 0;
    min-width: 250px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: 0 8px 24px rgba(15, 23, 42, .14), 0 2px 6px rgba(15, 23, 42, .08);
    padding: 14px;
    z-index: 30;
    display: flex;
    flex-direction: column;
    gap: 12px;
    }

    .popover[hidden] { display: none; }

    .popover-section {
    display: flex;
    flex-direction: column;
    gap: 8px;
    }

    .popover-label {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: .04em;
    color: var(--text-muted);
    }

    .popover-row {
    display: flex;
    align-items: center;
    gap: 8px;
    }

    .popover-actions { justify-content: flex-end; }

    .popover .form-select { width: 100%; }

    .popover-divider {
    height: 1px;
    background: var(--border);
    margin: 2px 0;
    }

    /* ---- Main Area ---- */
    #main {
    grid-row: 2;
    grid-column: 1;
    position: relative;
    overflow: hidden;
    }

    /* ---- Chart Panel ---- */
    /* The chart always fills the full main area; the detail panel slides in
       as an overlay on top of it rather than reserving horizontal space. */
    #chart-panel {
    position: absolute;
    inset: 0;
    overflow: hidden;
    background: #fff;
    cursor: grab;
    }

    #chart-panel:active { cursor: grabbing; }

    #chart-panel svg {
    width: 100%;
    height: 100%;
    display: block;
    }

    /* ---- Detail Panel (right) ----
       Overlays the chart from the right. Hidden off-screen by default and
       slid into view when a service is selected (.visible). */
    #detail-panel {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    width: var(--panel-w);
    background: var(--surface);
    border-left: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    overflow-x: hidden;
    box-shadow: -4px 0 16px rgba(0, 0, 0, .12);
    transform: translateX(100%);
    transition: transform 260ms cubic-bezier(.4, 0, .2, 1);
    will-change: transform;
    z-index: 5;
    }

    #detail-panel.visible {
    transform: translateX(0);
    }

    #detail-panel .empty-state {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 8px;
    color: var(--text-muted);
    padding: 24px;
    text-align: center;
    }

    #detail-panel .empty-state i { font-size: 36px; opacity: .5; }

    /* ============================================================
    Buttons
    ============================================================ */
    .btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 14px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    transition: all var(--transition);
    white-space: nowrap;
    border: 1px solid transparent;
    }

    .btn i { font-size: 12px; }

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

    .btn-outline {
    background: var(--surface);
    color: var(--text);
    border-color: var(--border);
    }
    .btn-outline:hover {
    background: var(--bg);
    border-color: #cbd5e1;
    }

    .btn-ghost {
    background: transparent;
    color: var(--text-secondary);
    }
    .btn-ghost:hover {
    background: var(--bg);
    color: var(--text);
    }

    .btn-danger-text {
    background: transparent;
    color: var(--danger);
    padding: 4px 8px;
    font-size: 12px;
    }
    .btn-danger-text:hover {
    background: #fef2f2;
    color: var(--danger-hover);
    }

    .btn-icon {
    width: 32px; height: 32px;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    }
    .btn-icon:hover { background: var(--bg); color: var(--text); }

    .btn-sm { padding: 4px 10px; font-size: 12px; }
    .btn-xs { padding: 2px 7px;  font-size: 11px; }
    .btn-reset { font-size: 11px; }

    /* Disabled controls: dimmed and non-interactive (replaces per-button
       inline opacity that used to be toggled from JS). */
    button:disabled {
    opacity: 0.4;
    cursor: default;
    pointer-events: none;
    }

    /* ============================================================
    Form Elements
    ============================================================ */
    .form-select, .form-input {
    height: 34px;
    padding: 0 10px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-size: 13px;
    outline: none;
    transition: border-color var(--transition);
    }
    .form-select:focus, .form-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(59,130,246,.12);
    }

    .time-filter-label {
    font-size: 12px;
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
    }

    .block-toggle {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    font-size: 12px;
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
    cursor: pointer;
    }
    .block-toggle input { cursor: pointer; }

    .block-length-input { width: 64px; }

    .time-filter-dash {
    color: var(--text-muted);
    font-size: 13px;
    margin: 0 2px;
    }

    .time-filter-input {
    width: 110px;
    height: 30px;
    padding: 0 8px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text);
    font-family: var(--font-mono);
    font-size: 12px;
    text-align: center;
    outline: none;
    transition: border-color var(--transition);
    }
    .time-filter-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(59,130,246,.12);
    }
    .time-filter-input::placeholder {
    color: var(--text-muted);
    font-size: 10px;
    }

    .form-select {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2364748b' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 10px center;
    padding-right: 28px;
    }

    .form-input { width: 100%; }

    /* File inputs: flex-center the native "Choose File" button inside the box
       and restyle it to match the app's buttons. Purely cosmetic — the native
       picker behaviour is kept (reliable across browsers, incl. Safari). */
    .form-input[type="file"] {
    display: flex;
    align-items: center;
    font-size: 12px;
    color: var(--text-secondary);
    }
    .form-input[type="file"]::file-selector-button {
    margin: 3px 12px 0 0;
    padding: 5px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--bg);
    color: var(--text);
    font-family: var(--font);
    font-size: 12px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    }
    .form-input[type="file"]::file-selector-button:hover {
    background: var(--accent-light);
    border-color: #cbd5e1;
    color: var(--accent-hover);
    }

    .form-label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 4px;
    text-transform: uppercase;
    letter-spacing: .03em;
    }

    .form-group { margin-bottom: 12px; }

    .form-row {
    display: flex;
    gap: 8px;
    }
    .form-row > * { flex: 1; }

    .color-swatch {
    width: 28px; height: 28px;
    border-radius: 50%;
    border: 2px solid var(--border);
    cursor: pointer;
    transition: transform var(--transition);
    }
    .color-swatch:hover { transform: scale(1.15); }
    .color-swatch.selected {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px var(--accent-light);
    }

    .color-palette {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
    }

    /* ============================================================
    Modal / Overlay
    ============================================================ */
    .modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(15,23,42,.35);
    backdrop-filter: blur(2px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
    animation: fadeIn 120ms ease;
    }

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

    .modal {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    width: 440px;
    max-width: 94vw;
    max-height: 85vh;
    overflow-y: auto;
    animation: slideUp 180ms ease;
    }

    /* Add Service Plan modal has more inner controls — give it extra room */
    #modal-add-plan .modal {
    width: 540px;
    }

    @keyframes slideUp {
    from { transform: translateY(12px); opacity: 0; }
    to   { transform: translateY(0);    opacity: 1; }
    }

    .modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border);
    }

    .modal-header h2 {
    font-size: 16px;
    font-weight: 600;
    }

    .modal-body { padding: 20px; }

    .modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 8px;
    padding: 14px 20px;
    border-top: 1px solid var(--border);
    }

    /* ============================================================
    Detail Panel Content
    ============================================================ */
    .detail-header {
    padding: 16px;
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 8px;
    }

    .detail-header .service-info h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 2px;
    }

    .detail-header .service-info .meta {
    font-size: 12px;
    color: var(--text-secondary);
    }

    .badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 99px;
    font-size: 11px;
    font-weight: 600;
    letter-spacing: .02em;
    }
    .badge-north { background: #dbeafe; color: #1d4ed8; }
    .badge-south { background: #fce7f3; color: #be185d; }

    /* ---- Per-service signaling blocks group ---- */
    .detail-blocks {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    gap: 10px;
    }

    .blocks-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 8px;
    }

    .blocks-title {
    font-size: 13px;
    font-weight: 600;
    color: var(--text);
    display: inline-flex;
    align-items: center;
    gap: 6px;
    }

    .blocks-title i { color: var(--text-muted); }

    .blocks-length {
    display: flex;
    align-items: center;
    gap: 8px;
    }

    .blocks-length-label {
    font-size: 12px;
    color: var(--text-secondary);
    flex: 1;
    }

    .blocks-length-unit { font-size: 12px; color: var(--text-muted); }

    /* Modern on/off switch */
    .switch {
    position: relative;
    display: inline-block;
    width: 40px;
    height: 22px;
    flex: none;
    cursor: pointer;
    }

    .switch input {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
    }

    .switch-slider {
    position: absolute;
    inset: 0;
    background: var(--border);
    border-radius: 999px;
    transition: background var(--transition);
    }

    .switch-slider::before {
    content: '';
    position: absolute;
    width: 18px;
    height: 18px;
    left: 2px;
    top: 2px;
    background: #fff;
    border-radius: 50%;
    box-shadow: 0 1px 2px rgba(0, 0, 0, .25);
    transition: transform var(--transition);
    }

    .switch input:checked + .switch-slider { background: var(--accent); }
    .switch input:checked + .switch-slider::before { transform: translateX(18px); }
    .switch input:focus-visible + .switch-slider { box-shadow: 0 0 0 3px var(--accent-light); }

    .detail-table-wrap {
    padding: 8px 16px 16px;
    flex: 1;
    overflow-y: auto;
    }

    .detail-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13px;
    }

    .detail-table th {
    font-size: 11px;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: .03em;
    text-align: left;
    padding: 6px 4px;
    border-bottom: 2px solid var(--border);
    }

    .detail-table td {
    padding: 4px;
    border-bottom: 1px solid #f1f5f9;
    color: var(--text);
    font-variant-numeric: tabular-nums;
    }

    .detail-table .station-name {
    font-weight: 500;
    max-width: 110px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    }

    .detail-table input.time-input {
    width: 72px;
    height: 28px;
    padding: 0 6px;
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    background: transparent;
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--text);
    text-align: center;
    transition: all var(--transition);
    }
    .detail-table input.time-input:hover {
    border-color: var(--border);
    }
    .detail-table input.time-input:focus {
    border-color: var(--accent);
    background: var(--accent-light);
    outline: none;
    box-shadow: 0 0 0 2px rgba(59,130,246,.1);
    }

    /* ============================================================
    Plans List in Edit Modal
    ============================================================ */
    .plan-list-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    margin-bottom: 8px;
    transition: all var(--transition);
    }
    .plan-list-item:hover { border-color: #cbd5e1; }
    .plan-list-item.hidden { opacity: .45; }

    .plan-list-item .plan-color {
    width: 16px; height: 16px;
    border-radius: 3px;
    flex-shrink: 0;
    cursor: pointer;
    border: 1px solid rgba(0,0,0,.12);
    transition: transform var(--transition), box-shadow var(--transition);
    }
    .plan-list-item .plan-color:hover {
    transform: scale(1.15);
    box-shadow: 0 0 0 2px var(--accent-light);
    }
    .plan-list-item .plan-color .plan-color-input {
    position: absolute;
    width: 0; height: 0;
    opacity: 0;
    pointer-events: none;
    }

    .plan-list-item .plan-name {
    flex: 1;
    font-weight: 500;
    font-size: 13px;
    }
    .plan-list-item .plan-name-input {
    width: 100%;
    font: inherit;
    font-weight: 500;
    color: inherit;
    background: transparent;
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    padding: 2px 4px;
    margin: -2px -4px;
    transition: border-color var(--transition), background var(--transition);
    }
    .plan-list-item .plan-name-input:hover {
    border-color: var(--border);
    }
    .plan-list-item .plan-name-input:focus {
    outline: none;
    background: #fff;
    border-color: var(--accent);
    }

    /* ============================================================
    Chart Legend
    ============================================================ */
    #chart-legend {
    position: absolute;
    top: 10px;
    left: 10px;
    width: max-content;
    max-width: calc(100% - 20px);
    background: rgba(255,255,255,.92);
    border-radius: var(--radius-sm);
    padding: 6px 10px;
    font-size: 11px;
    display: flex;
    flex-wrap: wrap;
    gap: 8px 16px;
    pointer-events: none;
    box-shadow: var(--shadow);
    }

    #chart-legend .legend-item {
    display: flex;
    align-items: center;
    gap: 4px;
    }

    #chart-legend .legend-swatch {
    width: 10px; height: 10px;
    border-radius: 2px;
    }

    /* ============================================================
    Tooltip
    ============================================================ */
    #chart-tooltip {
    position: absolute;
    pointer-events: none;
    background: rgba(15,23,42,.88);
    color: #fff;
    font-size: 12px;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    opacity: 0;
    transition: opacity 100ms;
    z-index: 20;
    white-space: nowrap;
    }

    /* ============================================================
    Upload Zone
    ============================================================ */
    #upload-overlay {
    position: fixed;
    inset: 0;
    background: rgba(248,250,252,.9);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 50; /* above chart, below modals (100) so Add Plan modal sits on top */
    }

    .upload-card {
    background: var(--surface);
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 48px 64px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: var(--shadow);
    }

    .upload-card:hover {
    border-color: var(--accent);
    background: var(--accent-light);
    }

    .upload-card i {
    font-size: 48px;
    color: var(--accent);
    margin-bottom: 16px;
    }

    .upload-card h2 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 6px;
    }

    .upload-card p {
    font-size: 13px;
    color: var(--text-secondary);
    }

    /* ============================================================
    Toast
    ============================================================ */
    #toast {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background: var(--text);
    color: #fff;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    opacity: 0;
    transform: translateY(10px);
    transition: all 200ms ease;
    z-index: 300;
    pointer-events: none;
    }
    #toast.show { opacity: 1; transform: translateY(0); }
    #toast.error { background: var(--danger); }

    /* ============================================================
    Misc
    ============================================================ */
    .drag-cursor { cursor: ew-resize !important; }

    .axis text {
    font-size: 10px;
    fill: var(--text-muted);
    font-family: var(--font);
    }

    .axis line, .axis .domain {
    stroke: var(--border);
    }

    .grid line {
    stroke: #f1f5f9;
    stroke-dasharray: 2 4;
    }

    .grid .domain { display: none; }

    /* Signaling-block occupancy rectangles (drawn beneath the service lines).
       Translucent fill in the service colour; non-interactive so they never
       intercept line clicks or chart panning. */
    .block-rect {
    fill-opacity: 0.12;
    stroke-opacity: 0.35;
    stroke-width: 0.5;
    pointer-events: none;
    }

    .service-path {
    fill: none;
    stroke-width: 1.8;
    stroke-linejoin: round;
    stroke-linecap: round;
    opacity: 0.78;
    cursor: pointer;
    transition: stroke-width 80ms ease, opacity 80ms ease;
    }
    .service-path:hover { stroke-width: 3; opacity: 1; }
    .service-path.selected { stroke-width: 3.2; opacity: 1; cursor: ew-resize; }
    .service-path.selected:hover { stroke-width: 3.2; }

    .service-hitarea {
    fill: none;
    stroke: transparent;
    stroke-width: 14;
    cursor: pointer;
    }
    .service-hitarea.selected { cursor: ew-resize; }

    .node-dot {
    cursor: ew-resize;
    stroke: #fff;
    stroke-width: 1.5;
    }
    .node-dot:hover { r: 6.5; }

    /* Scrollbar styling */
    ::-webkit-scrollbar { width: 6px; }
    ::-webkit-scrollbar-track { background: transparent; }
    ::-webkit-scrollbar-thumb {
    background: #cbd5e1;
    border-radius: 3px;
    }
    ::-webkit-scrollbar-thumb:hover { background: #94a3b8; }