:root {
    --bg-core: #0f172a;
    --bg-panel: #1e293b;
    --bg-interactive: #334155;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --danger: #ef4444;
    --danger-hover: #b91c1c;
    --success: #10b981;
    --border: #475569;
    --font-stack: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.3), 0 2px 4px -2px rgb(0 0 0 / 0.3);
    
    /* Peak Colors for distinct environments */
    --env-A: #f87171;
    --env-B: #60a5fa;
    --env-C: #34d399;
    --env-D: #fbbf24;
    --env-E: #a78bfa;
    --env-F: #f472b6;
    --env-G: #2dd4bf;
    --env-H: #eab308;
    --env-I: #c084fc;
    --env-J: #fb923c;
}

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

body {
    background-color: var(--bg-core);
    color: var(--text-main);
    font-family: var(--font-stack);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.app-header {
    background-color: var(--bg-panel);
    border-bottom: 1px solid var(--border);
    padding: 1rem 2rem;
    box-shadow: var(--shadow);
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.header-content h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-main);
    letter-spacing: -0.025em;
}

.header-controls {
    display: flex;
    gap: 0.5rem;
}

/* Buttons */
.btn {
    padding: 0.5rem 1rem;
    border-radius: 0.375rem;
    border: none;
    font-weight: 500;
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: var(--font-stack);
}

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

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

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

.btn-action { background-color: var(--success); color: white; }
.btn-action:hover { filter: brightness(1.1); }

/* Main Layout */
.app-container {
    display: flex;
    flex-direction: column;
    flex: 1;
    max-width: 1600px;
    margin: 0 auto;
    padding: 1.5rem;
    gap: 1.5rem;
    width: 100%;
}

@media (min-width: 1024px) {
    .app-container {
        flex-direction: row;
    }
}

.panel {
    background-color: var(--bg-panel);
    border-radius: 0.75rem;
    border: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    box-shadow: var(--shadow);
}

.left-panel { flex: 1; min-width: 350px; max-width: 500px; }
.right-panel { flex: 2; min-width: 0; }

.panel-header {
    background-color: rgba(0,0,0,0.2);
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.panel-header h2 {
    font-size: 1.125rem;
    font-weight: 600;
}

/* Controls */
.builder-controls, .spectrum-controls {
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    border-bottom: 1px solid var(--border);
}

.spectrum-controls {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.control-group label {
    font-size: 0.875rem;
    color: var(--text-muted);
    font-weight: 500;
}

.slider, .slider-small {
    width: 100%;
    accent-color: var(--accent);
}

.dropdown {
    padding: 0.5rem;
    border-radius: 0.375rem;
    background-color: var(--bg-core);
    border: 1px solid var(--border);
    color: var(--text-main);
    font-family: var(--font-stack);
}

/* Functional Groups Palette */
.fx-palette {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.fx-btn {
    padding: 0.375rem 0.75rem;
    background-color: var(--bg-core);
    border: 1px solid var(--border);
    border-radius: 0.375rem;
    color: var(--text-main);
    cursor: pointer;
    font-size: 0.875rem;
    transition: all 0.2s;
}

.fx-btn:hover {
    border-color: var(--accent);
}

.fx-btn.active {
    background-color: var(--accent);
    border-color: var(--accent);
    color: white;
}

/* Molecule Viewer */
.molecule-viewer-container {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border);
    background-color: white; /* White background for clear chemical diagram */
    color: black;
    text-align: center;
    position: relative;
    min-height: 200px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    overflow: auto;
}

.molecule-viewer-container h3 {
    position: absolute;
    top: 0.5rem;
    left: 0.5rem;
    font-size: 0.75rem;
    color: #666;
    text-transform: uppercase;
}

.molecule-viewer {
    position: relative;
    display: inline-block;
    padding: 2rem;
}

/* Carbon Nodes */
.node-c {
    display: inline-block;
    position: relative;
    font-weight: 600;
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.25rem;
    border-radius: 4px;
    transition: background-color 0.2s;
    user-select: none;
}

.node-c:hover, .node-c.highlight {
    background-color: rgba(59, 130, 246, 0.2);
}

/* Environment List */
.environments-list-container {
    padding: 1.5rem;
    flex: 1;
    overflow-y: auto;
}

.environments-list-container h3 {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
    text-transform: uppercase;
}

.env-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.env-item {
    padding: 0.75rem;
    background-color: var(--bg-interactive);
    border-radius: 0.375rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    cursor: pointer;
    transition: transform 0.1s, box-shadow 0.1s;
}

.env-item:hover, .env-item.highlight {
    transform: translateX(4px);
    box-shadow: -4px 0 0 0 var(--accent);
}

.env-color {
    width: 16px;
    height: 16px;
    border-radius: 50%;
    flex-shrink: 0;
}

.env-details {
    display: flex;
    flex-direction: column;
}

.env-label { font-weight: 600; font-size: 0.875rem; }
.env-desc { font-size: 0.75rem; color: var(--text-muted); }

/* Tabs */
.tabs {
    display: flex;
    gap: 0.25rem;
    background-color: var(--bg-core);
    padding: 0.25rem;
    border-radius: 0.5rem;
}

.tab-btn {
    padding: 0.5rem 1rem;
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-weight: 600;
    cursor: pointer;
    border-radius: 0.375rem;
    transition: all 0.2s;
}

.tab-btn:hover { color: var(--text-main); }
.tab-btn.active {
    background-color: var(--bg-interactive);
    color: var(--text-main);
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

/* Spectrum Canvas */
.canvas-container {
    padding: 1rem;
    background-color: #fafafa;
    border-bottom: 1px solid var(--border);
    position: relative;
    display: flex;
    justify-content: center;
    overflow-x: auto;
}

canvas {
    max-width: 100%;
    height: auto;
    background: white;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    border-radius: 4px;
}

.spectrum-tooltip {
    position: absolute;
    background: rgba(0,0,0,0.8);
    color: white;
    padding: 0.5rem;
    border-radius: 4px;
    font-size: 0.75rem;
    pointer-events: none;
    z-index: 10;
}

/* Toggles & Checkboxes */
.toggles {
    flex-direction: row;
    align-items: center;
    gap: 1.5rem;
}

.toggle-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.875rem !important;
}

/* Peak Table */
.peak-table-container {
    padding: 1.5rem;
    overflow-y: auto;
    flex: 1;
}

.peak-table-container h3 {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
    text-transform: uppercase;
}

.peak-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.875rem;
}

.peak-table th, .peak-table td {
    padding: 0.75rem;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

.peak-table th {
    color: var(--text-muted);
    font-weight: 500;
}

.peak-table tr {
    cursor: pointer;
    transition: background-color 0.2s;
}

.peak-table tr:hover, .peak-table tr.highlight {
    background-color: var(--bg-interactive);
}

.peak-color-cell {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.peak-color-dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
}

/* Utilities */
.hidden { display: none !important; }

/* Tooltip implementation for D2O */
.tooltip {
    position: relative;
    display: inline-block;
}

.tooltip .tooltiptext {
    visibility: hidden;
    width: 180px;
    background-color: var(--bg-core);
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px;
    position: absolute;
    z-index: 10;
    bottom: 125%;
    left: 50%;
    margin-left: -90px;
    opacity: 0;
    transition: opacity 0.3s;
    font-size: 0.75rem;
    font-weight: normal;
    border: 1px solid var(--border);
}

.tooltiptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: var(--border) transparent transparent transparent;
}

.tooltip:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
}

/* Modal */
.modal {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.7);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 100;
}

.modal-content {
    background: var(--bg-panel);
    padding: 2rem;
    border-radius: 0.5rem;
    width: 90%;
    max-width: 500px;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    border: 1px solid var(--border);
}

#json-textarea {
    width: 100%;
    background: var(--bg-core);
    color: var(--text-main);
    border: 1px solid var(--border);
    border-radius: 0.375rem;
    padding: 0.75rem;
    font-family: monospace;
    font-size: 0.875rem;
    resize: vertical;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
}