:root {
    /* Architecture Blue & Core Red Theme */
    --app-bg: #fdfbf7;
    --panel-bg: rgba(255, 255, 255, 0.85);
    --glass-border: rgba(41, 128, 185, 0.15);
    --text-primary: #2c3e50;
    --text-secondary: #7f8c8d;

    --arch-blue: #2980b9;
    --core-red: #c0392b;
    --growth-green: #27ae60;
    --future-gold: #f39c12;

    --shadow-sm: 0 4px 6px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 20px rgba(0, 0, 0, 0.08);

    --font-family: "Noto Serif SC", "Outfit", serif;
    --font-mono: "JetBrains Mono", monospace;
    --font-title: "Ma Shan Zheng", cursive;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--app-bg);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    background-image: url('https://images.unsplash.com/photo-1486406146926-c627a92ad1ab?q=80&w=2670&auto=format&fit=crop');
    background-size: cover;
    background-position: center;
}

.app-container {
    width: 95vw;
    height: 90vh;
    max-width: 1600px;
    background: rgba(255, 252, 245, 0.96);
    backdrop-filter: blur(20px);
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* Header */
.main-header {
    padding: 1.2rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--glass-border);
    background: rgba(255, 255, 255, 0.6);
}

.header-content h1 {
    font-family: var(--font-title);
    font-size: 2rem;
    font-weight: 400;
    color: var(--arch-blue);
}

.highlight {
    color: var(--core-red);
}

.subtitle {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-style: italic;
    margin-top: -5px;
}

.apple-btn {
    padding: 10px 16px;
    border-radius: 10px;
    border: 1px solid rgba(0, 0, 0, 0.1);
    background: #fff;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 6px;
    font-weight: 600;
}

.apple-btn:hover {
    background: #f5f5f5;
    transform: scale(1.05);
}

/* Main Stage */
.main-stage {
    flex-grow: 1;
    display: grid;
    grid-template-columns: 1fr 380px;
    gap: 2px;
    background: rgba(0, 0, 0, 0.02);
    overflow: hidden;
}

.diagram-panel,
.analysis-panel {
    background: var(--panel-bg);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    position: relative;
}

.panel-header {
    padding: 16px 24px;
    border-bottom: 1px solid var(--glass-border);
    background: rgba(255, 255, 255, 0.5);
}

.panel-header h3 {
    font-size: 1.2rem;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.panel-sub {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-family: var(--font-mono);
}

/* Diagram */
.diagram-container {
    flex-grow: 1;
    position: relative;
    overflow: hidden;
    background-image:
        radial-gradient(rgba(41, 128, 185, 0.1) 1px, transparent 1px);
    background-size: 30px 30px;
}

.diagram-svg {
    width: 100%;
    height: 100%;
}

/* Nodes */
.node-group {
    cursor: pointer;
    transition: all 0.3s ease;
}

.node-rect {
    fill: #fff;
    stroke: var(--arch-blue);
    stroke-width: 2px;
    rx: 6;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.05));
    transition: all 0.3s ease;
}

.node-group:hover .node-rect {
    stroke: var(--core-red);
    stroke-width: 3px;
    filter: drop-shadow(0 4px 8px rgba(192, 57, 43, 0.2));
    transform: translateY(-2px);
}

.node-group.selected .node-rect {
    fill: var(--arch-blue);
    stroke: var(--arch-blue);
}

.node-group.selected text {
    fill: #fff;
}

/* Highlights */
.node-group.highlight-red .node-rect {
    stroke: var(--core-red);
    stroke-width: 3px;
    fill: #fff0f0;
    filter: drop-shadow(0 0 12px rgba(192, 57, 43, 0.4));
}

.node-group.highlight-gold .node-rect {
    stroke: var(--future-gold);
    stroke-width: 3px;
    fill: #fffdf0;
    filter: drop-shadow(0 0 12px rgba(243, 156, 18, 0.4));
}

.node-group.highlight-green .node-rect {
    stroke: var(--growth-green);
    stroke-width: 3px;
    fill: #f0fff4;
    filter: drop-shadow(0 0 12px rgba(39, 174, 96, 0.4));
}

.node-text {
    font-size: 13px;
    font-weight: 600;
    fill: var(--text-primary);
    text-anchor: middle;
    pointer-events: none;
}

/* Edges */
.edge {
    stroke: var(--arch-blue);
    stroke-width: 1.5px;
    opacity: 0.2;
    fill: none;
    transition: all 0.5s ease;
}

.edge.highlight {
    stroke: var(--core-red);
    stroke-width: 2.5px;
    opacity: 0.8;
}

/* Toolbar */
.toolbar {
    padding: 16px;
    display: flex;
    justify-content: center;
    gap: 16px;
    background: rgba(255, 255, 255, 0.8);
    border-top: 1px solid var(--glass-border);
}

.tool-group {
    display: flex;
    gap: 8px;
    align-items: center;
}

.tool-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    writing-mode: vertical-lr;
    text-orientation: upright;
    letter-spacing: 2px;
    margin-right: 4px;
    font-weight: 600;
    opacity: 0.6;
}

.tool-divider {
    width: 1px;
    background: rgba(0, 0, 0, 0.1);
    margin: 0 8px;
}

.tool-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    padding: 8px 12px;
    background: #fff;
    border: 1px solid rgba(0, 0, 0, 0.1);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
    min-width: 70px;
}

.tool-btn:hover {
    background: #f0f8ff;
    transform: translateY(-2px);
    border-color: var(--arch-blue);
}

.tool-btn .icon {
    font-size: 1.2rem;
}

.tool-btn span:last-child {
    font-size: 0.7rem;
    color: var(--text-secondary);
}

/* Analysis Panel */
.analysis-panel {
    padding: 24px;
    gap: 20px;
    overflow-y: auto;
}

.concept-card,
.insight-card,
.selection-info {
    background: #fff;
    border-radius: 16px;
    padding: 20px;
    box-shadow: var(--shadow-sm);
    border: 1px solid rgba(0, 0, 0, 0.05);
}

.concept-card {
    border-top: 4px solid var(--arch-blue);
}

.card-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
}

.card-icon {
    font-size: 1.6rem;
}

.card-header h4 {
    font-size: 1.1rem;
    color: var(--text-primary);
}

.card-desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 16px;
}

.math-box {
    background: rgba(41, 128, 185, 0.05);
    padding: 12px;
    border-radius: 8px;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--arch-blue);
    text-align: center;
    border: 1px dashed rgba(41, 128, 185, 0.3);
}

/* Insight */
.insight-card {
    background: linear-gradient(135deg, #fff5f5 0%, #fff 100%);
    border: 1px solid rgba(192, 57, 43, 0.2);
}

.insight-card h4 {
    color: var(--core-red);
    margin-bottom: 10px;
    font-size: 1rem;
}

.insight-card p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Selection Info */
.selection-info h4 {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.empty-selection {
    font-style: italic;
    color: #bdc3c7;
    font-size: 0.85rem;
    padding: 10px 0;
}

.selected-tag {
    display: inline-block;
    padding: 4px 10px;
    background: rgba(41, 128, 185, 0.1);
    color: var(--arch-blue);
    border-radius: 12px;
    font-size: 0.8rem;
    margin: 0 6px 6px 0;
    border: 1px solid rgba(41, 128, 185, 0.2);
}

.action-hint {
    font-size: 0.8rem;
    color: var(--core-red);
    font-style: italic;
    margin-top: 10px;
    padding-top: 10px;
    border-top: 1px dashed rgba(0, 0, 0, 0.1);
}

/* Tooltip */
.tooltip {
    position: absolute;
    background: rgba(255, 255, 255, 0.95);
    padding: 12px;
    border-radius: 8px;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
    pointer-events: none;
    opacity: 0;
    transition: opacity 0.2s;
    font-size: 0.85rem;
    border: 1px solid rgba(0, 0, 0, 0.05);
    z-index: 100;
    max-width: 220px;
}