/* Custom Scrollbar */
        ::-webkit-scrollbar {
            width: 8px;
            height: 8px;
        }

        ::-webkit-scrollbar-track {
            background: #f8f9fa;
        }

        ::-webkit-scrollbar-thumb {
            background: #dee2e6;
            border-radius: 4px;
        }

        ::-webkit-scrollbar-thumb:hover {
            background: #adb5bd;
        }

        /* Chart Specific Styles */
        .chart-container {
            width: 100%;
            height: 3650px;
            background: #ffffff;
            /* FIXED background URL */
            background-image: url("https://www.transparenttextures.com/patterns/cubes.png");
            background-size: auto;
            /* optional */
            background-repeat: repeat;
            /* optional */

            border-radius: 12px;
            /* box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06); */
            margin: 1.5rem auto;

            position: relative;
            overflow: hidden;

            display: flex;
            align-items: flex-start;
            /* keeps chart locked to top */
            justify-content: center;
        }

        .chart-container:active {
            cursor: grabbing;
        }

        /* Node Hover Effects */
        .node {
            cursor: pointer;
        }

        .node rect.card-bg {
            transition: all 0.2s ease;
        }

        .node:hover rect.card-bg {
            filter: drop-shadow(0 4px 6px rgba(0, 0, 0, 0.15)) !important;
            stroke: #cbd5e1;
            /* slate-300 */
        }

        /* Floating control bar over chart */
        .controls-overlay {
            position: absolute;
            top: 10px;
            left: 50%;
            transform: translateX(-50%);
            z-index: 20;
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
        }

        /* Better mobile spacing */
        @media (max-width:768px) {
            .chart-container {
                height: 1750px;
            }

            .controls-overlay {
                top: 6px;
                width: 96%;
                justify-content: space-between;
            }

            .controls-overlay .btn {
                padding: .25rem .45rem;
                font-size: 12px;
            }
        }

        .icon-btn {
            background: transparent;
            border: none;
            padding: .85rem;
            border-radius: 8px;
            color: #334155;
            transition: background .15s, transform .08s;
        }

        .icon-btn:hover {
            background: #e5e7eb;
        }

        .icon-btn:active {
            background: #d1d5db;
            transform: scale(.94);
        }

        .icon {
            width: 20px;
            height: 20px;
            stroke: currentColor;
            stroke-width: 2;
            fill: none;
        }

        .btn-icon {
            width: 36px;
            height: 36px;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 0;
            color: #495057;
        }

        .btn-icon:hover {
            color: #0d6efd;
            background-color: #f8f9fa;
        }

        /* Sidebar Link Active State Override */
        .list-group-item.active {
            z-index: 2;
            color: #0d6efd;
            background-color: #e7f1ff;
            border-color: transparent;
            border-left: 4px solid #0d6efd;
        }

        .list-group-item {
            border-left: 4px solid transparent;
            border-right: none;
            border-top: none;
            border-bottom: none;
        }

        .banner-overlay {
            background: rgba(0, 0, 0, 0.4);
        }

        /* ======================================================
           RESPONSIVE BREAKPOINT TUNING
           (360, 430, 540, 768, 820, 1024)
        ====================================================== */

        /* Base defaults (desktop ≥1024) */
        .chart-container {
            height: 3650px;
        }

        /* 1024px — small laptop */
        @media(max-width:1024px) {
            .chart-container {
                height: 2900px;
            }
        }

        /* 820px — tablets landscape */
        @media(max-width:820px) {
            .chart-container {
                height: 2400px;
            }
        }

        /* 768px — tablets portrait */
        @media(max-width:768px) {
            .chart-container {
                height: 2220px;
            }

            .icon-btn {
                padding: .65rem;
            }
        }

        /* 540px — large mobile */
        @media(max-width:540px) {
            .chart-container {
                height: 1550px;
            }

            .icon-btn {
                padding: .55rem;
            }

            .controls-overlay {
                width: 96%;
            }
        }

        /* 430px — medium mobile */
        @media(max-width:430px) {
            .chart-container {
                height: 1500px;
            }

            .icon {
                width: 18px;
                height: 18px;
            }

            .icon-btn {
                padding: .45rem;
            }
        }

        /* 360px — small mobile */
        @media(max-width:360px) {
            .chart-container {
                height: 1450px;
            }

            .icon {
                width: 16px;
                height: 16px;
            }

            .icon-btn {
                padding: .35rem;
            }
        }