:root {
            --primary-color: #2c3e50;
            --secondary-color: #34495e;
            --accent-color: #3498db;
            --bg-color: #f8f9fa;
            --card-bg: #ffffff;
            --border-color: #dee2e6;
            --text-color: #333333;
            --text-light: #6c757d;
            --danger-color: #e74c3c;
            --success-color: #2ecc71;
            --menu-bg: #ffffff;
            --menu-hover: #e8f4f8;
            --panel-bg: #e8f4f8;
            --panel-border: #bce8f1;
            --highlight-bg: #f1f3f5;
            --table-hover: #f1f3f5;
            --input-bg: #ffffff;
            --table-highlight-bg: #f8fbff;
            --box-bg: #f9f9f9;
            --box-border: #cccccc;
            --print-header-bg: #f8f9fa;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
            background-color: var(--bg-color);
            color: var(--text-color);
            line-height: 1.6;
            margin: 0;
            padding: 20px;
        }

        .structure-container {
            background-color: white;
            border: 1px solid var(--border-color);
            border-radius: 8px;
            margin-bottom: 20px;
            padding: 10px;
            text-align: center;
            box-shadow: 0 2px 4px rgba(0,0,0,0.05);
            overflow: hidden;
            display: none; /* hidden by default until sequence added */
        }
        
        #peptideCanvas {
            max-width: 100%;
            height: auto;
        }

        .container {
            max-width: 1400px;
            margin: 0 auto;
            display: grid;
            grid-template-columns: 380px 1fr;
            gap: 20px;
            align-items: start;
        }

        h1 {
            grid-column: 1 / -1;
            text-align: center;
            color: var(--primary-color);
            margin-bottom: 30px;
            border-bottom: 2px solid var(--accent-color);
            padding-bottom: 10px;
        }

        .card {
            background: var(--card-bg);
            border-radius: 8px;
            padding: 20px;
            box-shadow: 0 4px 6px rgba(0,0,0,0.05);
            border: 1px solid var(--border-color);
            margin-bottom: 20px;
        }

        h2 {
            font-size: 1.1rem;
            color: var(--secondary-color);
            margin-top: 0;
            margin-bottom: 15px;
            border-bottom: 1px solid var(--border-color);
            padding-bottom: 10px;
        }

        .form-group {
            margin-bottom: 15px;
        }
        
        .form-group.row {
            display: grid;
            grid-template-columns: 120px 1fr;
            align-items: center;
            gap: 10px;
        }

        .form-group.nested {
            margin-left: 15px;
            border-left: 3px solid var(--accent-color);
            padding-left: 10px;
            margin-top: -5px;
        }

        label {
            font-weight: 500;
            color: var(--secondary-color);
            font-size: 0.95rem;
            display: block;
            margin-bottom: 5px;
        }

        .form-group.row label {
            margin-bottom: 0;
        }

        input[type="number"], input[type="text"], select {
            width: 100%;
            padding: 8px 10px;
            border: 1px solid var(--border-color);
            border-radius: 4px;
            box-sizing: border-box;
            font-size: 0.95rem;
            background-color: var(--input-bg);
            color: var(--text-color);
        }
        
        input:focus, select:focus {
            outline: none;
            border-color: var(--accent-color);
            box-shadow: 0 0 0 2px rgba(52, 152, 219, 0.2);
        }

        .input-with-unit {
            display: flex;
            align-items: center;
            gap: 5px;
        }

        .input-with-unit input {
            flex-grow: 1;
        }

        .unit {
            color: var(--text-light);
            font-size: 0.85rem;
            width: 45px;
            text-align: right;
        }

        button {
            background-color: var(--accent-color);
            color: white;
            border: none;
            padding: 8px 15px;
            border-radius: 4px;
            cursor: pointer;
            font-size: 0.95rem;
            font-weight: 500;
            transition: background-color 0.2s;
            width: 100%;
        }

        button:hover {
            background-color: #2980b9;
        }

        button.btn-danger {
            background-color: var(--danger-color);
            width: auto;
            padding: 4px 8px;
            font-size: 0.85rem;
        }
        button.btn-danger:hover {
            background-color: #c0392b;
        }
        
        button.btn-success {
            background-color: var(--success-color);
        }
        button.btn-success:hover {
            background-color: #27ae60;
        }

        /* Results Panel */
        .summary-box {
            display: grid;
            grid-template-columns: repeat(5, 1fr);
            gap: 15px;
            margin-bottom: 20px;
            background-color: var(--panel-bg);
            padding: 15px;
            border-radius: 6px;
            border: 1px solid var(--panel-border);
        }

        .summary-item {
            display: flex;
            flex-direction: column;
        }

        .summary-label {
            font-size: 0.85rem;
            color: var(--secondary-color);
            font-weight: bold;
        }

        .summary-value {
            font-size: 1.2rem;
            color: var(--accent-color);
            font-weight: bold;
        }

        .table-responsive {
            overflow: visible; /* Changed to visible for dropdown flyouts */
        }

        table {
            width: 100%;
            border-collapse: collapse;
            background: var(--card-bg);
            font-size: 0.9rem;
        }

        th, td {
            padding: 12px 8px;
            text-align: center !important;
            border-bottom: 1px solid var(--border-color);
            vertical-align: middle;
        }

        /* Ensure content inside td is centered even with nested elements */
        td > div {
            margin: 0 auto;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        th {
            background-color: var(--primary-color);
            color: white;
            font-weight: 500;
            white-space: nowrap;
        }
        
        tr:hover {
            background-color: #f1f3f5;
        }

        .step-badge {
            background-color: var(--secondary-color);
            color: white;
            padding: 2px 6px;
            border-radius: 12px;
            font-size: 0.8rem;
            font-weight: bold;
        }

        .hidden {
            display: none !important;
        }

        .hint {
            font-size: 0.8rem;
            color: var(--text-light);
            margin-top: 5px;
            display: block;
        }

        input.table-input {
            width: 60px;
            padding: 4px;
            font-size: 0.85rem;
            text-align: center;
        }
        
        /* Drag and Drop */
        .drag-handle { 
            cursor: grab; 
            color: #bdc3c7; 
            margin-right: 8px; 
            font-size: 1.1rem; 
        }
        .drag-handle:active { cursor: grabbing; }
        .draggable-row { transition: background-color 0.1s; }
        .draggable-row.dragging { opacity: 0.4; background-color: #f1f3f5; }
        .draggable-row.drag-over { border-top: 2px solid var(--accent-color); }
        .draggable-row.drag-over-bottom { border-bottom: 2px solid var(--accent-color); }

        /* Cascading Dropdown (ChemDraw Style) */
        .spps-dropdown {
            position: relative;
            display: inline-block;
            min-width: 140px;
        }
        .spps-btn {
            width: 100%;
            padding: 6px 10px;
            background: var(--input-bg);
            border: 1px solid var(--border-color);
            border-radius: 4px;
            text-align: center;
            cursor: pointer;
            display: flex;
            justify-content: center; 
            align-items: center;
            gap: 5px;
            font-family: inherit;
            font-size: 0.9rem;
            color: var(--text-color);
        }
        .spps-btn:focus {
            border-color: var(--accent-color);
            box-shadow: 0 0 0 2px rgba(52, 152, 219, 0.2);
        }
        .spps-btn-text {
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
        }
        .spps-menu {
            display: none;
            position: absolute;
            top: 100%;
            left: 0;
            z-index: 9999;
            background: var(--menu-bg);
            border: 1px solid #ccc;
            box-shadow: 2px 2px 6px rgba(0,0,0,0.2);
            padding: 4px 0;
            margin-top: 2px;
            border-radius: 2px;
        }
        .spps-menu-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            width: 320px;
        }
        .spps-item {
            position: relative;
            padding: 6px 20px 6px 15px;
            cursor: default;
            font-size: 0.9rem;
            color: #333;
            user-select: none;
            text-align: left;
        }
        .spps-item:hover {
            background-color: var(--menu-hover);
        }
        .spps-has-sub::after {
            content: '▶';
            font-size: 0.6rem;
            color: #999;
            position: absolute;
            right: 8px;
            top: 50%;
            transform: translateY(-50%);
        }
        .spps-submenu {
            display: none;
            position: absolute;
            top: -5px;
            left: 100%; 
            z-index: 10000;
            background: var(--menu-bg);
            border: 1px solid #ccc;
            box-shadow: 2px 2px 6px rgba(0,0,0,0.2);
            padding: 4px 0;
            min-width: 200px;
            border-radius: 2px;
            white-space: nowrap;
        }
        .spps-item:hover > .spps-submenu {
            display: block;
        }
        .spps-subitem {
            padding: 6px 15px;
            cursor: pointer;
            font-size: 0.9rem;
            display: flex;
            justify-content: space-between;
            gap: 15px;
            text-align: left;
        }
        .spps-subitem:hover {
            background-color: var(--accent-color);
            color: white;
        }
        .spps-subitem:hover .mw-hint {
            color: #e0f2fe;
        }
        .spps-divider {
            height: 1px;
            background-color: #e5e5e5;
            margin: 4px 0;
            grid-column: 1 / -1;
        }
        .mw-hint {
            font-size: 0.85em;
            color: #888;
        }

        @media (max-width: 992px) {
            .container { grid-template-columns: 1fr; }
            .table-responsive { overflow-x: auto; } /* restore scrolling on mobile */
            .summary-box { grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); }
        }

        /* --- Print Styles --- */
        .print-header { display: none; }
        @media print {
            body { background: white; padding: 0; margin: 0; color: #000; font-size: 11pt; }
            h1 { font-size: 1.5rem; margin-bottom: 15px; border-bottom: 2px solid #000; }
            .left-panel, .hint, .drag-handle, .delete-btn, .btn-danger, .btn-success, #btnAddSingle, .structure-controls { display: none !important; }
            .container { display: block; max-width: 100%; padding: 0; margin: 0; }
            .right-panel { width: 100%; }
            .card { box-shadow: none; border: none; padding: 0; margin-bottom: 10px; }
            
            .print-header { 
                display: block; 
                margin-bottom: 20px; 
                border: 2px solid #000; 
                padding: 15px; 
                border-radius: 8px;
            }
            .print-header-row { display: flex; justify-content: space-between; margin-bottom: 10px; align-items: center; }
            .print-header-field { border-bottom: 1px dashed #666; flex-grow: 1; margin: 0 10px; }

            .summary-box { background: white; border: 1px solid #000; grid-template-columns: repeat(5, 1fr) !important; }
            #targetSequenceDisplay { background: white; border: 1px solid #000; color: #000 !important; }
            #lblTargetSeq { color: #000 !important; }

            table { border: 1px solid #000; text-align: center; }
            th { background-color: #f1f3f5 !important; color: #000 !important; border: 1px solid #000; text-align: center; }
            td { border: 1px solid #ccc; text-align: center; }
            th:last-child, td:last-child { display: none; } /* Hide Action column */
            
            /* Clean up interactive elements for print */
            input, select { border: none !important; appearance: none; -webkit-appearance: none; background: transparent !important; color: #000; font-weight: bold; text-align: center; }
            .spps-btn { border: none !important; background: transparent !important; padding: 0 !important; color: #000; font-weight: bold; width: auto; justify-content: center; }
            .spps-btn span:last-child { display: none; } /* Hide arrow */
            .reset-custom-link { display: none; }
            .step-badge { background: transparent; color: #000; border: 1px solid #000; }
        }

/* Canvas Zoom/Pan Specifics */
.structure-container {
    cursor: grab;
    position: relative;
}
.structure-container:active {
    cursor: grabbing;
}
#peptideSvg {
    transform-origin: center center;
}

/* Custom Context Menu */
.custom-context-menu {
    position: fixed;
    z-index: 100000;
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
    border-radius: 8px;
    padding: 6px 0;
    min-width: 170px;
    display: none;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    font-size: 0.9rem;
    animation: fadeInMenu 0.12s ease-out;
}

@keyframes fadeInMenu {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.custom-context-menu-item {
    padding: 8px 16px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-color);
    transition: background-color 0.2s, color 0.2s;
    text-align: left;
}

.custom-context-menu-item:hover {
    background-color: var(--accent-color);
    color: white;
}

/* Toast Notification */
.toast-notification {
    position: fixed;
    bottom: 35px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: rgba(44, 62, 80, 0.95);
    color: white;
    padding: 10px 22px;
    border-radius: 30px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    z-index: 100001;
    font-size: 0.9rem;
    font-weight: 500;
    opacity: 0;
    transition: opacity 0.3s, transform 0.3s;
    pointer-events: none;
}

.toast-notification.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}