:root[data-theme="dark"] {
    --bg-color: #0d1117;
    --text-color: #c9d1d9;
    --card-bg: rgba(22, 27, 34, 0.7);
    --border-color: rgba(48, 54, 61, 0.8);
    --primary-color: #58a6ff;
    --primary-hover: #3182ce;
    --secondary-color: rgba(139, 148, 158, 0.2);
    --secondary-hover: rgba(139, 148, 158, 0.3);
    --input-bg: rgba(1, 4, 9, 0.8);
    --input-border: #30363d;
    
    /* Node Colors */
    --node-bg: #161b22;
    --node-border: #30363d;
    --node-scan: #238636;
    --node-index: #d29922;
    --node-join: #bc8cff;
    --node-sort: #f78166;
    --node-bottleneck: rgba(248, 81, 73, 0.2);
    --node-bottleneck-border: #f85149;
    
    --radius: 12px;
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --glass-border: 1px solid rgba(255, 255, 255, 0.05);
    
    --font-sans: 'Inter', -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, monospace;
}

:root[data-theme="light"] {
    --bg-color: #f6f8fa;
    --text-color: #24292f;
    --card-bg: rgba(255, 255, 255, 0.8);
    --border-color: rgba(208, 215, 222, 0.8);
    --primary-color: #0969da;
    --primary-hover: #0550ae;
    --secondary-color: rgba(175, 184, 193, 0.2);
    --secondary-hover: rgba(175, 184, 193, 0.3);
    --input-bg: #ffffff;
    --input-border: #d0d7de;
    
    /* Node Colors */
    --node-bg: #ffffff;
    --node-border: #d0d7de;
    --node-scan: #1a7f37;
    --node-index: #bf8700;
    --node-join: #8250df;
    --node-sort: #cf222e;
    --node-bottleneck: rgba(207, 34, 46, 0.1);
    --node-bottleneck-border: #cf222e;
    
    --radius: 12px;
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.05);
    --glass-border: 1px solid rgba(0, 0, 0, 0.05);
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-sans);
    line-height: 1.5;
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
}

.app-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    height: 100vh;
}

header {
    flex-shrink: 0;
    border-radius: var(--radius);
    padding: 1rem 1.5rem;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--primary-color);
}

.logo h1 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-color);
    letter-spacing: -0.02em;
}

.actions {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

/* Glassmorphism */
.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
}

.glass {
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: var(--glass-border);
}

main {
    display: flex;
    gap: 1.5rem;
    flex: 1;
    min-height: 0; /* Important for flex child scrolling */
}

/* Sidebar */
.sidebar {
    width: 350px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    flex-shrink: 0;
    overflow-y: auto;
}

.input-section {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.section-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
}

.helper-text {
    font-size: 0.85rem;
    opacity: 0.8;
}

.helper-text code {
    font-family: var(--font-mono);
    background: var(--input-bg);
    padding: 0.1rem 0.3rem;
    border-radius: 4px;
    border: 1px solid var(--border-color);
}

textarea {
    background-color: var(--input-bg);
    border: 1px solid var(--input-border);
    color: var(--text-color);
    padding: 0.75rem;
    border-radius: 8px;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    resize: vertical;
    min-height: 200px;
    max-height: 400px;
    width: 100%;
    transition: border-color 0.2s;
}

textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.15);
}

.error-message {
    color: #f85149;
    font-size: 0.85rem;
    background: rgba(248, 81, 73, 0.1);
    padding: 0.75rem;
    border-radius: 6px;
    border: 1px solid rgba(248, 81, 73, 0.3);
}

.hidden {
    display: none !important;
}

/* Stats Section */
.stats-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-top: 1rem;
}

.stat-box {
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    padding: 0.75rem;
    border-radius: 8px;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.stat-label {
    font-size: 0.75rem;
    text-transform: uppercase;
    opacity: 0.7;
    letter-spacing: 0.05em;
}

.stat-value {
    font-size: 1.25rem;
    font-weight: 600;
    font-family: var(--font-mono);
}

.error-text {
    color: #f85149;
}

.hints-container {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.hints-container h3 {
    font-size: 1rem;
    margin-bottom: 0.75rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.hints-container h3::before {
    content: "💡";
}

#hints-list {
    list-style-type: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

#hints-list li {
    font-size: 0.85rem;
    padding: 0.75rem;
    background: var(--input-bg);
    border-left: 3px solid var(--primary-color);
    border-radius: 4px;
    line-height: 1.4;
}

/* Editor/Canvas Panel */
.editor-panel {
    flex: 1;
    display: flex;
    flex-direction: column;
    padding: 0;
    overflow: hidden; /* Contains the canvas */
    position: relative;
}

.panel-toolbar {
    padding: 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--card-bg);
    z-index: 10;
}

.zoom-controls {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

#zoom-level {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    min-width: 3rem;
    text-align: center;
}

.legend {
    display: flex;
    gap: 1rem;
    font-size: 0.8rem;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.color-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
}

.color-dot.safe { background: var(--node-scan); }
.color-dot.warning { background: var(--node-index); }
.color-dot.danger { background: var(--node-join); }
.color-dot.highlight { 
    background: var(--node-bottleneck); 
    border: 1px solid var(--node-bottleneck-border);
}

.canvas-container {
    flex: 1;
    overflow: auto;
    background-color: var(--input-bg);
    position: relative;
    cursor: grab; /* Enable panning */
}

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

.empty-state {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    opacity: 0.5;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

/* Tree Structure */
.tree-wrapper {
    position: relative;
    min-width: 100%;
    min-height: 100%;
    padding: 3rem;
    transform-origin: top left;
    transition: transform 0.1s ease-out;
}

/* Nodes */
.tree-node-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    padding: 20px 5px 0 5px;
}

.tree-node-children {
    display: flex;
    justify-content: center;
    padding-top: 20px;
    position: relative;
}

.tree-node {
    background: var(--node-bg);
    border: 1px solid var(--node-border);
    border-radius: 8px;
    padding: 1rem;
    width: 260px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    position: relative;
    z-index: 2;
    transition: all 0.2s ease;
    cursor: default;
}

.tree-node:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.15);
    border-color: var(--primary-color);
}

.tree-node.bottleneck {
    background: var(--node-bottleneck);
    border-color: var(--node-bottleneck-border);
}

.node-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border-color);
}

.node-meta {
    display: flex;
    flex-direction: column;
}

.node-type {
    font-weight: 600;
    font-size: 0.95rem;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.node-type::before {
    content: '';
    display: inline-block;
    width: 10px;
    height: 10px;
    border-radius: 2px;
}

.node-type.type-scan::before { background: var(--node-scan); }
.node-type.type-index::before { background: var(--node-index); }
.node-type.type-join::before { background: var(--node-join); }
.node-type.type-sort::before { background: var(--node-sort); }
.node-type.type-other::before { background: var(--text-color); }

.node-relation {
    font-size: 0.7rem;
    opacity: 0.7;
    margin-top: 0.2rem;
    text-transform: uppercase;
}

.node-cost-badge {
    background: var(--input-bg);
    border: 1px solid var(--border-color);
    padding: 0.2rem 0.5rem;
    border-radius: 12px;
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--primary-color);
    font-weight: 600;
}

.bottleneck .node-cost-badge {
    color: #f85149;
    border-color: rgba(248, 81, 73, 0.4);
}

.node-stats {
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    font-family: var(--font-mono);
    font-size: 0.8rem;
}

.stat-row {
    display: flex;
    justify-content: space-between;
}

.stat-name {
    opacity: 0.7;
}

.stat-val {
    font-weight: 500;
}

/* Lines for Tree */
/* SVG implementation is generally better for dynamic trees, but CSS lines work for strict DOM trees */
.tree-node-wrapper::before, .tree-node-wrapper::after, .tree-node-children::before {
    content: '';
    position: absolute;
    background-color: var(--border-color);
}

/* Vertical line above node */
.tree-node-wrapper::before {
    width: 2px;
    height: 20px;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
}

/* Horizontal line connecting siblings */
.tree-node-wrapper::after {
    height: 2px;
    top: 0;
    /* width is calculated dynamically or handled via SVG overlay */
}

/* Vertical line below parent to children */
.tree-node-children::before {
    width: 2px;
    height: 20px;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
}

/* Root node has no top line */
.tree-root > .tree-node-wrapper::before,
.tree-root > .tree-node-wrapper::after {
    display: none;
}

/* Popover */
.node-popover {
    position: absolute;
    width: 300px;
    border-radius: 8px;
    z-index: 100;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    pointer-events: none;
}

.popover-header {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.popover-header h4 {
    font-size: 0.95rem;
    margin: 0;
}

.badge {
    font-size: 0.75rem;
    font-family: var(--font-mono);
    background: var(--primary-color);
    color: white;
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
}

.popover-body {
    padding: 1rem;
}

.details-grid {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    font-size: 0.8rem;
}

.detail-row {
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
}

.detail-key {
    opacity: 0.7;
    font-weight: 500;
}

.detail-val {
    font-family: var(--font-mono);
    word-break: break-all;
}

.detail-val.code {
    background: var(--input-bg);
    padding: 0.3rem;
    border-radius: 4px;
    border: 1px solid var(--border-color);
    margin-top: 0.2rem;
}

/* UI Elements */
.badge.primary { background: var(--primary-color); color: #fff; }

/* Buttons */
button {
    font-family: var(--font-sans);
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: 6px;
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.primary-button {
    background-color: var(--primary-color);
    color: white;
    border: 1px solid rgba(0,0,0,0.1);
    padding: 0.75rem 1rem;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.primary-button:hover:not(:disabled) {
    background-color: var(--primary-hover);
}

.full-width {
    width: 100%;
}

.secondary-button {
    background-color: var(--secondary-color);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
}

.secondary-button:hover:not(:disabled) {
    background-color: var(--secondary-hover);
}

.icon-button {
    background: transparent;
    border: 1px solid transparent;
    color: var(--text-color);
    padding: 0.5rem;
    opacity: 0.8;
}

.icon-button:hover:not(:disabled) {
    opacity: 1;
    background-color: var(--secondary-color);
    border-radius: 6px;
}

.icon-button.outline {
    border: 1px solid var(--border-color);
}

/* Theme Icons */
[data-theme="dark"] .sun-icon { display: none; }
[data-theme="light"] .moon-icon { display: none; }

/* SVG Lines Layer */
#tree-lines {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 1;
}

.tree-line {
    stroke: var(--border-color);
    stroke-width: 2px;
    fill: none;
}