:root {
    --bg-gradient: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    --text-color: #333;
    --text-muted: #666;
    --panel-bg: rgba(255, 255, 255, 0.7);
    --panel-border: rgba(0, 0, 0, 0.1);
    --input-bg: rgba(255, 255, 255, 0.9);
    --input-border: rgba(0, 0, 0, 0.2);
    --btn-bg: rgba(0, 0, 0, 0.05);
    --btn-border: rgba(0, 0, 0, 0.1);
    --btn-text: #333;
    --map-face-bg: #ccc;
    --map-cell-bg: #fff;
    --sol-bg: rgba(0, 0, 0, 0.05);
    --sol-span-bg: rgba(102, 126, 234, 0.2);
    --sol-span-text: #333;
    --tab-text: #666;
    --tab-active-bg: rgba(102, 126, 234, 0.2);
    --tab-active-text: #333;
    --scramble-btn-border: rgba(102, 126, 234, 0.5);
    --cube-status-color: #333;
    --btn-hover-bg: rgba(0, 0, 0, 0.1);
    --scrollbar-track: rgba(0, 0, 0, 0.05);
}

[data-theme="dark"] {
    --bg-gradient: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    --text-color: #eee;
    --text-muted: #aaa;
    --panel-bg: rgba(255, 255, 255, 0.05);
    --panel-border: rgba(255, 255, 255, 0.1);
    --input-bg: rgba(0, 0, 0, 0.3);
    --input-border: rgba(255, 255, 255, 0.2);
    --btn-bg: rgba(255, 255, 255, 0.1);
    --btn-border: rgba(255, 255, 255, 0.2);
    --btn-text: #fff;
    --map-face-bg: #000;
    --map-cell-bg: #222;
    --sol-bg: rgba(0, 0, 0, 0.4);
    --sol-span-bg: rgba(102, 126, 234, 0.3);
    --sol-span-text: #eee;
    --tab-text: #888;
    --tab-active-bg: rgba(102, 126, 234, 0.2);
    --tab-active-text: #fff;
    --scramble-btn-border: rgba(102, 126, 234, 0.5);
    --cube-status-color: #ddd;
    --btn-hover-bg: rgba(255, 255, 255, 0.2);
    --scrollbar-track: rgba(255, 255, 255, 0.05);
}

/* Theme Switch Styles */
.theme-switch-wrapper {
    display: flex;
    align-items: center;
}

.theme-switch {
    display: inline-block;
    height: 34px;
    position: relative;
    width: 60px;
}

.theme-switch input {
    display: none;
}

.slider {
    background-color: #ccc;
    bottom: 0;
    cursor: pointer;
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
    transition: .4s;
}

.slider:before {
    background-color: #fff;
    bottom: 4px;
    content: "";
    height: 26px;
    left: 4px;
    position: absolute;
    transition: .4s;
    width: 26px;
}

input:checked + .slider {
    background-color: #66bb6a;
}

input:checked + .slider:before {
    transform: translateX(26px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-gradient);
    min-height: 100vh;
    color: var(--text-color);
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 30px;
}

header h1 {
    font-size: 2.5rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    margin-bottom: 10px;
}

header p {
    color: var(--text-muted);
    font-size: 1rem;
}

/* Main Layout */
.main-content {
    display: flex;
    flex-wrap: wrap;
    gap: 30px;
    justify-content: center;
}

/* 3D Cube Container */
.cube-container {
    flex: 1;
    min-width: 400px;
    height: 500px;
    background: var(--panel-bg);
    border-radius: 20px;
    backdrop-filter: blur(10px);
    border: 1px solid var(--panel-border);
    overflow: hidden;
    position: relative;
}

/* Trạng thái trên khối Cube */
.cube-status {
    position: absolute;
    bottom: 20px;
    left: 0;
    width: 100%;
    text-align: center;
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--cube-status-color);
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.8);
    pointer-events: none; /* Không cản trở việc dùng chuột xoay cube */
    z-index: 10;
    transition: color 0.3s ease;
}
.status-scrambling { color: #ffcc00; }
.status-solving { color: #667eea; text-shadow: 0 0 10px rgba(102, 126, 234, 0.8); }
.status-solved { color: #00cc00; text-shadow: 0 0 10px rgba(0, 204, 0, 0.8); }

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

/* Control Panel */
.control-panel {
    flex: 1;
    min-width: 350px;
    background: var(--panel-bg);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 25px;
    border: 1px solid var(--panel-border);
}

.input-group {
    margin-bottom: 25px;
}

.input-group label {
    display: block;
    margin-bottom: 10px;
    font-weight: 600;
    color: var(--cube-status-color);
}

.input-group input {
    width: 100%;
    padding: 12px 15px;
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: 10px;
    color: var(--btn-text);
    font-size: 1rem;
    font-family: monospace;
    margin-bottom: 15px;
}

.input-group input:focus {
    outline: none;
    border-color: #667eea;
}

.button-group {
    display: flex;
    gap: 15px;
}

.btn {
    flex: 1;
    padding: 12px 20px;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-random {
    background: var(--btn-bg);
    color: var(--btn-text);
    border: 1px solid var(--input-border);
}

.btn-random:hover {
    background: var(--btn-hover-bg);
    transform: translateY(-2px);
}

.btn-solve {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
    margin-top: 20px;
    width: 100%;
}

.btn-solve:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

/* CSS cho nút Perform Scramble */
.btn-scramble {
    background: var(--panel-bg);
    color: var(--btn-text);
    border: 1px solid var(--scramble-btn-border); /* Viền màu xanh tím */
}

/* Tabs Styling */
.tab-header {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--panel-border);
    padding-bottom: 10px;
}

.tab-btn {
    flex: 1;
    background: transparent;
    color: var(--tab-text);
    border: none;
    padding: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s;
}

.tab-btn.active {
    background: var(--tab-active-bg);
    color: var(--btn-text);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Color Picker Section */
.color-picker-section label {
    display: block;
    margin-bottom: 10px;
    font-weight: 600;
    color: var(--cube-status-color);
}

.palette {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    justify-content: center;
}

.color-swatch {
    width: 35px;
    height: 35px;
    border-radius: 8px;
    cursor: pointer;
    border: 3px solid transparent;
    transition: transform 0.2s;
}

.color-swatch:hover {
    transform: scale(1.1);
}

.color-swatch.active {
    border-color: var(--btn-text);
    box-shadow: 0 0 10px rgba(255, 255, 255, 0.5);
}

/* Bản đồ trải phẳng 2D (Facelet Map) */
.facelet-map {
    display: grid;
    grid-template-columns: repeat(4, 60px);
    grid-template-rows: repeat(3, 60px);
    gap: 5px;
    justify-content: center;
    margin: 20px 0;
}

.map-face {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 2px;
    background: var(--map-face-bg);
    padding: 2px;
    border-radius: 4px;
}

.map-cell {
    background: var(--map-cell-bg);
    border-radius: 2px;
    cursor: crosshair;
    transition: filter 0.2s;
}

.map-cell:hover {
    filter: brightness(1.2);
}

.btn-scramble:hover {
    background: var(--tab-active-bg);
    transform: translateY(-2px);
}

/* CSS làm nút Giải ngay to và nổi bật hơn khi nằm một mình */
.btn-large {
    width: 100%;
    margin-bottom: 20px;
    padding: 15px;
    font-size: 1.2rem;
    letter-spacing: 1px;
}

.btn-small {
    padding: 5px 12px;
    background: var(--btn-bg);
    border: 1px solid var(--input-border);
    border-radius: 6px;
    color: var(--cube-status-color);
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.btn-small:hover {
    background: var(--btn-hover-bg);
}

/* Result Panel */
.result-panel {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--panel-border);
}

.result-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

.result-header span {
    font-weight: 600;
    color: #667eea;
}

.solution-moves {
    background: var(--sol-bg);
    border-radius: 10px;
    padding: 15px;
    max-height: 200px;
    overflow-y: auto;
    font-family: monospace;
    font-size: 1rem;
    line-height: 1.8;
    margin-bottom: 15px;
}

.solution-moves span {
    display: inline-block;
    background: var(--sol-span-bg);
    padding: 4px 10px;
    margin: 3px;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
}

.solution-moves span:hover {
    background: rgba(102, 126, 234, 0.6);
    transform: scale(1.05);
}

.solution-moves span.current-move {
    background: #667eea;
    color: white;
    box-shadow: 0 0 10px rgba(102, 126, 234, 0.5);
}

.solution-stats {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 15px;
}

.animation-control {
    display: flex;
    gap: 10px;
}

.hidden {
    display: none;
}

/* Footer */
footer {
    text-align: center;
    margin-top: 40px;
    padding-top: 20px;
    color: #666;
    font-size: 0.8rem;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--panel-bg);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb {
    background: rgba(102, 126, 234, 0.5);
    border-radius: 10px;
}

/* Responsive */
@media (max-width: 900px) {
    .main-content {
        flex-direction: column;
    }
    
    .cube-container {
        min-width: auto;
        height: 400px;
    }
    
    header h1 {
        font-size: 1.8rem;
    }
}

/* Settings Button */
.settings-btn {
    position: absolute;
    top: 20px;
    right: 20px;
    background: var(--panel-bg);
    border: 1px solid var(--panel-border);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
    z-index: 100;
}
.settings-btn:hover {
    transform: rotate(90deg);
    background: var(--btn-hover-bg);
}

/* Modal Styling */
.modal {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    opacity: 1;
    transition: opacity 0.3s;
}
.modal.hidden {
    opacity: 0;
    pointer-events: none;
}
.modal-content {
    background: var(--panel-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--panel-border);
    border-radius: 12px;
    width: 350px;
    padding: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    transform: translateY(0);
    transition: transform 0.3s;
}
.modal.hidden .modal-content {
    transform: translateY(-20px);
}
.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--panel-border);
    padding-bottom: 10px;
    margin-bottom: 20px;
}
.modal-header h2 {
    font-size: 1.2rem;
    color: var(--text-color);
}
.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-muted);
    cursor: pointer;
}
.close-btn:hover {
    color: var(--text-color);
}

.setting-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}
.setting-item > label {
    font-weight: 600;
    color: var(--text-color);
}

/* Ubuntu style number input */
.number-input {
    display: flex;
    align-items: center;
    border: 1px solid var(--panel-border);
    border-radius: 6px;
    overflow: hidden;
    background: var(--input-bg);
}
.num-btn {
    background: var(--btn-bg);
    color: var(--text-color);
    border: none;
    width: 30px;
    height: 30px;
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: background 0.2s;
}
.num-btn:hover {
    background: var(--btn-hover-bg);
}
.number-input input[type=number] {
    width: 60px;
    height: 30px;
    border: none;
    background: transparent;
    color: var(--text-color);
    text-align: center;
    font-family: monospace;
    font-size: 1rem;
    -moz-appearance: textfield;
}
.number-input input[type=number]::-webkit-outer-spin-button,
.number-input input[type=number]::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}