:root {
    --bg-color: #020617;
    --accent-color: #38bdf8;
    --secondary-accent: #f472b6;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --glass-bg: rgba(15, 23, 42, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
    --node-bg: #1e293b;
    --edge-color: #334155;
    --font-main: 'Outfit', sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    --scrollbar-bg: rgba(255, 255, 255, 0.05);
    --scrollbar-thumb: rgba(255, 255, 255, 0.2);
}

[data-theme="light"] {
    --bg-color: #f8fafc;
    --accent-color: #0ea5e9;
    --secondary-accent: #db2777;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(0, 0, 0, 0.1);
    --node-bg: #e2e8f0;
    --edge-color: #94a3b8;
    --scrollbar-bg: rgba(0, 0, 0, 0.05);
    --scrollbar-thumb: rgba(0, 0, 0, 0.2);
}

* {
    scrollbar-width: thin;
    scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-bg);
}

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

*::-webkit-scrollbar-track {
    background: var(--scrollbar-bg);
}

*::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 4px;
}

*::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.3);
}

[data-theme="light"] *::-webkit-scrollbar-thumb:hover {
    background: rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: var(--font-main);
    background: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    background-image: 
        radial-gradient(circle at 20% 20%, rgba(56, 189, 248, 0.05) 0%, transparent 40%),
        radial-gradient(circle at 80% 80%, rgba(244, 114, 182, 0.05) 0%, transparent 40%);
}

.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 0;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    border-bottom: 1px solid var(--glass-border);
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    flex: 1;
}

@keyframes pulse-ring {
    0% { transform: scale(1); opacity: 1; }
    100% { transform: scale(2.5); opacity: 0; }
}

.logo-img {
    height: 32px;
    width: auto;
}

[data-theme="light"] .logo-img {
    filter: invert(1);
}

main {
    display: flex;
    flex: 1;
    overflow: hidden;
    background: rgba(0, 0, 0, 0.1);
}

#controls {
    width: 320px;
    min-width: 300px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    padding: 1.5rem;
    overflow-y: auto;
    border-right: 1px solid rgba(255, 255, 255, 0.05);
}

#visualization {
    flex: 1;
    position: relative;
    overflow: hidden; /* Prevent redundant scrollbars */
    background: rgba(0, 0, 0, 0.2);
    display: flex;
    align-items: center;
    justify-content: center;
}

#tree-canvas {
    display: block;
    max-width: 100%;
    max-height: 100%;
}

#resizer {
    width: 4px;
    cursor: col-resize;
    background: rgba(255, 255, 255, 0.05);
    transition: background 0.2s, width 0.2s;
    z-index: 10;
}

#resizer:hover, #resizer:active {
    background: var(--accent-color);
    width: 6px;
}

#insights {
    width: 380px;
    min-width: 250px;
    display: flex;
    flex-direction: column;
    padding: 0;
    overflow: hidden;
    border-left: 1px solid rgba(255, 255, 255, 0.05);
}

#code-panel, #stack-panel {
    display: flex;
    flex-direction: column;
    padding: 0;
    overflow: hidden;
}

#code-panel {
    flex: 1;
    min-height: 150px;
}

#stack-panel {
    flex: 0 0 300px; /* Default height to comfortably show 5-6 items */
    min-height: 150px;
    border-top: 1px solid rgba(255, 255, 255, 0.05);
}

#v-resizer {
    height: 4px;
    cursor: row-resize;
    background: rgba(255, 255, 255, 0.05);
    transition: background 0.2s, height 0.2s;
    z-index: 10;
}

#v-resizer:hover, #v-resizer:active {
    background: var(--accent-color);
    height: 6px;
}

#code-display {
    background: #1e1e1e !important; /* Base background matches atom-one-dark */
    padding: 0 !important;
    margin: 0;
    font-size: 0.85rem;
    flex: 1;
    overflow: auto;
    display: flex;
    flex-direction: column;
}

[data-theme="light"] #code-display {
    background: #fafafa !important; /* Base background matches atom-one-light */
}

#code-display code {
    display: inline-block;
    min-width: 100%;
    padding: 1rem 0; /* Move padding here so background extends */
    background: inherit;
}

#stack-display {
    flex: 1;
    overflow-y: auto;
}

#tree-canvas {
    width: 100%;
    height: 100%;
}

.control-group h3 {
    font-size: 0.9rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.control-group-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1rem;
}

.btn-regenerate {
    background: transparent;
    border: 1px solid var(--glass-border);
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 1rem;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    transition: color 0.2s, border-color 0.2s, transform 0.3s;
}

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

.btn-regenerate.spinning {
    animation: spin-once 0.4s ease-out;
}

@keyframes spin-once {
    from { transform: rotate(0deg); }
    to   { transform: rotate(360deg); }
}

.input-row, .toggle-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.8rem;
    font-size: 0.9rem;
    gap: 1rem;
}

.range-controls {
    display: flex;
    flex-direction: column;
    gap: 2px;
    flex: 1;
}

input[type="range"] {
    width: 100%;
    accent-color: var(--accent-color);
}

#depth-range, #child-range {
    min-width: 50px;
    text-align: right;
    font-weight: 600;
    color: var(--accent-color);
}

.btn-primary {
    width: 100%;
    padding: 0.8rem;
    background: var(--accent-color);
    color: var(--bg-color);
    border: none;
    border-radius: 0;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-primary:hover {
    filter: brightness(1.1);
    transform: translateY(-1px);
}

.btn-secondary {
    padding: 0.5rem 1rem;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    color: var(--text-primary);
    border-radius: 0;
    cursor: pointer;
    text-decoration: none;
    font-size: 0.9rem;
    transition: background 0.15s, color 0.15s;
}

[data-theme="light"] .btn-secondary {
    background: rgba(0, 0, 0, 0.05);
}

.btn-secondary:active,
#btn-step:active,
#btn-reset:active {
    background: #10b981 !important;
    color: #020617 !important;
    border-color: #10b981 !important;
}

.playback-controls {
    display: flex;
    gap: 8px;
    margin-top: 0.5rem;
}

.playback-controls button {
    flex: 1;
}

.btn-play {
    color: white;
    border: none;
    border-radius: 0;
    padding: 0.5rem;
    cursor: pointer;
    transition: background 0.2s;
    /* Default (Start / Restart) = green — action starts playback */
    background: #10b981;
}

.btn-play--paused {
    background: var(--accent-color); /* blue — indicates paused, click to resume */
}

select {
    width: 100%;
    background: var(--node-bg);
    color: var(--text-primary);
    border: 1px solid var(--glass-border);
    padding: 0.5rem;
    border-radius: 0;
    margin-bottom: 1rem;
}

.panel {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-height: 0;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 1.5rem 1rem 1.5rem;
    gap: 12px;
}

.header-actions {
    display: flex;
    gap: 8px;
    align-items: center;
    flex: 1;
    justify-content: flex-end;
}

.header-actions select {
    margin-bottom: 0;
    min-width: 120px;
}

.code-line {
    display: block;
    padding: 2px 1.5rem;
    border-radius: 0;
    transition: all 0.2s;
    white-space: pre; /* Ensure spaces aren't collapsed */
}

.code-line.highlight {
    background: rgba(56, 189, 248, 0.2);
    color: var(--accent-color);
    box-shadow: inset 3px 0 0 var(--accent-color);
}

.panel-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.8rem 1.5rem;
    background: rgba(255, 255, 255, 0.05);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.8rem;
    color: var(--text-secondary);
}

#lang-categories {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    flex: 1;
    min-width: 0;
}

.footer-controls {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 8px;
    flex-shrink: 0;
}

.lang-logo {
    height: 24px;
    width: auto;
    object-fit: contain;
    filter: drop-shadow(0 0 4px rgba(255, 255, 255, 0.1));
}

[data-theme="light"] .lang-logo {
    filter: drop-shadow(0 0 4px rgba(0, 0, 0, 0.1));
}

.category-badge {
    padding: 2px 8px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s;
    user-select: none;
    white-space: nowrap;
}

.category-badge:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: var(--accent-color);
}

.category-badge.active {
    background: var(--accent-color);
    color: var(--bg-color);
    border-color: var(--accent-color);
    font-weight: 600;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    user-select: none;
}


#stack-display {
    display: flex;
    flex-direction: column-reverse;
    gap: 4px;
    padding: 0 1.5rem 1.5rem 1.5rem;
    overflow-y: auto;
    overflow-x: hidden;
}

.stack-frame {
    padding: 8px 12px;
    background: rgba(56, 189, 248, 0.1);
    border-left: 3px solid var(--accent-color);
    border-radius: 0;
    font-size: 0.85rem;
    font-family: var(--font-mono);
    animation: slide-in 0.3s ease-out;
}

.stack-frame.active-visit {
    background: var(--primary-color);
    border-color: #fff;
    box-shadow: 0 0 15px var(--primary-color);
    transform: scale(1.05);
}

.print-result {
    font-size: 0.9rem;
    margin-left: 8px;
    font-weight: 800;
    color: #fff;
    text-shadow: 0 0 5px rgba(255, 255, 255, 0.5);
}

@keyframes slide-in {
    from { transform: translateX(20px); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

.stack-frame.exit-animation {
    transform: translateX(20px);
    opacity: 0;
    transition: all 0.2s ease-in;
}

#results-bar {
    height: 60px; /* Slightly shorter */
    margin: 0;
    padding: 0 2rem; /* Added horizontal padding to match header */
    border-left: none;
    border-right: none;
    border-bottom: none;
    display: flex;
    align-items: center;
}

.results-container {
    display: flex;
    align-items: center;
    gap: 1rem;
    width: 100%;
}

.results-container .label {
    color: var(--text-secondary);
    font-weight: 600;
}

#sequence-list {
    display: flex;
    gap: 8px;
    overflow-x: auto;
}

.seq-item {
    padding: 4px 12px;
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 0;
    font-weight: 600;
    transition: all 0.3s ease;
}

.seq-item.highlight-new {
    background: var(--accent-color);
    color: var(--bg-color);
    border-color: var(--accent-color);
    animation: pop 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    box-shadow: 0 0 10px var(--accent-color);
}

@keyframes pop {
    0% { transform: scale(0); }
    100% { transform: scale(1); }
}

/* SVG Styling */
.node {
    fill: var(--node-bg);
    stroke: var(--edge-color);
    stroke-width: 2;
    transition: all 0.3s;
}

.node.active {
    stroke: #ff4757;
    fill: #ff4757; /* Fill with red too for maximum visibility */
    filter: drop-shadow(0 0 10px rgba(255, 71, 87, 0.8));
}

.node.active + .node-label {
    fill: white;
}

.node.visited {
    fill: var(--node-bg); /* Keep it opaque to hide the edges */
    stroke: var(--accent-color);
}

.edge {
    stroke: var(--edge-color);
    stroke-width: 2;
    transition: stroke 0.3s;
}

.edge.active {
    stroke: var(--accent-color);
    stroke-width: 3;
}

.node-label {
    fill: var(--text-primary);
    font-size: 14px;
    font-weight: 600;
    pointer-events: none;
}

.btn-icon {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 1.2rem;
    padding: 4px 8px;
    border-radius: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.btn-icon:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.1);
}

[data-theme="light"] .btn-icon:hover {
    background: rgba(0, 0, 0, 0.1);
}

.hidden {
    display: none !important;
}

/* Dropdown Menu */
.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    right: 0;
    margin-top: 8px;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 8px 0;
    min-width: 150px;
    z-index: 1000;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

.dropdown-menu.show {
    display: flex;
    flex-direction: column;
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    cursor: pointer;
    color: var(--text-primary);
    transition: background 0.2s;
    user-select: none;
}

.dropdown-item input[type="checkbox"] {
    margin: 0;
}

.dropdown-item:hover {
    background: rgba(255, 255, 255, 0.05);
}

[data-theme="light"] .dropdown-item:hover {
    background: rgba(0, 0, 0, 0.05);
}