:root {
    /* Colors */
    --bg-color: #f5f5f5;
    --container-bg: white;
    --text-color: #333;
    --border-color: #ddd;
    --grid-border: #333;
    --cell-bg: white;
    --cell-given-bg: #f0f0f0;
    --cell-selected-bg: #d4e8ff;
    --cell-same-number-bg: #e6f3ff;
    --error-color: #e53935;
    --button-bg: #f0f0f0;
    --button-hover-bg: #e0e0e0;
    --primary-button-bg: #4CAF50;
    --primary-button-hover-bg: #45a049;
    --primary-button-text: white;
    --success-bg: #d4edda;
    --success-text: #155724;
    --error-bg: #f8d7da;
    --error-text: #721c24;
    --shadow-color: rgba(0, 0, 0, 0.1);

    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;

    /* Transitions */
    --transition-speed-fast: 0.15s;
    --transition-speed: 0.3s;
    --transition-speed-slow: 0.5s;
    --transition-function: cubic-bezier(0.4, 0, 0.2, 1); /* Material Design standard easing */
    --transition-function-bounce: cubic-bezier(0.175, 0.885, 0.32, 1.275); /* Bounce effect */
    --transition-function-ease-out: cubic-bezier(0.0, 0.0, 0.2, 1); /* Quick acceleration, gentle deceleration */
    --transition-function-ease-in: cubic-bezier(0.4, 0.0, 1, 1); /* Gentle acceleration, quick deceleration */
    --transition-function-sharp: cubic-bezier(0.4, 0, 0.6, 1); /* Quick acceleration and deceleration */

    /* Border Radius */
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;

    /* Font Sizes */
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-md: 1rem;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.5rem;

    /* Sizes */
    --container-width-sm: 95%;
    --container-width-md: 500px;
    --container-width-lg: 550px;
    --game-board-size-sm: 280px;
    --game-board-size-md: 350px;
    --game-board-size-lg: 400px;
    --game-board-size-xl: 450px;
}

.dark-mode {
    /* Colors */
    --bg-color: #121212;
    --container-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --border-color: #444;
    --grid-border: #666;
    --cell-bg: #2a2a2a;
    --cell-given-bg: #3a3a3a;
    --cell-selected-bg: #2c4f7c;
    --cell-same-number-bg: #253b5a;
    --error-color: #ff6b6b;
    --button-bg: #333;
    --button-hover-bg: #444;
    --primary-button-bg: #388e3c;
    --primary-button-hover-bg: #2e7d32;
    --primary-button-text: #e0e0e0;
    --success-bg: #1e4620;
    --success-text: #a5d6a7;
    --error-bg: #4a1515;
    --error-text: #f8c9c9;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Arial, sans-serif;
    transition: background-color var(--transition-speed) var(--transition-function),
                color var(--transition-speed) var(--transition-function),
                transform var(--transition-speed) var(--transition-function),
                box-shadow var(--transition-speed) var(--transition-function),
                border-color var(--transition-speed) var(--transition-function),
                opacity var(--transition-speed) var(--transition-function);
}

html {
    font-size: 16px;
    height: 100%;
}

body {
    background-color: var(--bg-color);
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100%;
    padding: 0;
    color: var(--text-color);
    line-height: 1.5;
    transition: background-color var(--transition-speed-slow) var(--transition-function);
    overflow-x: hidden;
}

.container {
    max-width: var(--container-width-lg);
    width: var(--container-width-sm);
    background-color: var(--container-bg);
    border-radius: var(--border-radius-lg);
    box-shadow: 0 4px 20px var(--shadow-color);
    padding: var(--spacing-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    margin: 0 auto;
    transition: all var(--transition-speed) var(--transition-function-ease-out);
    animation: fadeIn var(--transition-speed-slow) var(--transition-function-ease-out);
    overflow-x: hidden;
    min-height: 100vh;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

h1 {
    color: var(--text-color);
    margin-bottom: var(--spacing-lg);
    text-align: center;
    font-size: var(--font-size-xl);
    font-weight: 600;
}

h2 {
    color: var(--text-color);
    margin-bottom: var(--spacing-md);
    text-align: center;
    font-size: var(--font-size-lg);
    font-weight: 500;
}

.game-options {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
    gap: var(--spacing-md);
    align-items: center;
}

.difficulty select {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
    background-color: var(--cell-bg);
    color: var(--text-color);
    font-size: var(--font-size-sm);
    cursor: pointer;
    transition: border-color var(--transition-speed) var(--transition-function);
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right var(--spacing-sm) center;
    background-size: 1em;
    padding-right: var(--spacing-xl);
}

.difficulty select:hover, .difficulty select:focus {
    border-color: var(--primary-button-bg);
    outline: none;
}

.timer {
    font-size: var(--font-size-lg);
    font-weight: bold;
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--button-bg);
    border-radius: var(--border-radius-sm);
    color: var(--text-color);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.theme-toggle button, .sound-toggle button {
    background: none;
    border: none;
    font-size: var(--font-size-lg);
    cursor: pointer;
    color: var(--text-color);
    padding: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: transform 0.2s var(--transition-function),
                color 0.2s var(--transition-function);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle button:hover, .sound-toggle button:hover {
    transform: scale(1.1);
    color: var(--primary-button-bg);
}

.theme-toggle button:focus, .sound-toggle button:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: 2px;
}

.game-board {
    display: flex;
    flex-direction: column;
    background-color: var(--grid-border);
    border: 2px solid var(--grid-border);
    margin-bottom: var(--spacing-lg);
    width: 100%;
    max-width: var(--game-board-size-lg);
    aspect-ratio: 1/1;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    border-radius: var(--border-radius-sm);
    overflow: hidden;
    transition: all var(--transition-speed) var(--transition-function);
    animation: scaleIn var(--transition-speed) var(--transition-function-bounce);
    margin-left: auto;
    margin-right: auto;
}

@keyframes scaleIn {
    from { transform: scale(0.95); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

.row-group {
    display: flex;
    flex-direction: column;
    flex: 1;
    border-bottom: 2px solid var(--grid-border);
    transition: border-color var(--transition-speed) var(--transition-function);
}

.row-group:last-child {
    border-bottom: none;
}

.sudoku-row {
    display: flex;
    flex: 1;
}

.cell {
    background-color: var(--cell-bg);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: clamp(1rem, 3vw, var(--font-size-xl));
    font-weight: 500;
    cursor: pointer;
    user-select: none;
    position: relative;
    transition: all var(--transition-speed-fast) var(--transition-function);
    outline: none;
    flex: 1;
    border-right: 1px solid var(--grid-border);
    border-bottom: 1px solid var(--grid-border);
}

.cell:hover:not(.given) {
    background-color: rgba(212, 232, 255, 0.3);
}

.cell:last-child {
    border-right: none;
}

.sudoku-row:last-child .cell {
    border-bottom: none;
}

.cell:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: -2px;
    z-index: 2;
    box-shadow: inset 0 0 0 2px var(--primary-button-bg);
}

.cell:focus:not(:focus-visible) {
    outline: none;
    box-shadow: none;
}

.cell:focus-visible {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: -2px;
    z-index: 2;
}

.cell.given {
    font-weight: bold;
    background-color: var(--cell-given-bg);
}

.cell.selected {
    background-color: var(--cell-selected-bg);
    transform: scale(1.05);
    z-index: 1;
    box-shadow: 0 0 8px rgba(0, 0, 0, 0.2);
    animation: pulse 2s infinite var(--transition-function);
}

@keyframes pulse {
    0% { box-shadow: 0 0 0 0 rgba(66, 133, 244, 0.4); }
    70% { box-shadow: 0 0 0 6px rgba(66, 133, 244, 0); }
    100% { box-shadow: 0 0 0 0 rgba(66, 133, 244, 0); }
}

/* Animation for cell when a number is placed */
.cell.number-placed {
    animation: numberPlaced 0.5s var(--transition-function-bounce);
}

@keyframes numberPlaced {
    0% { transform: scale(1); }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); }
}

.cell.same-number {
    background-color: var(--cell-same-number-bg);
    animation: fadeBackground 0.5s var(--transition-function);
}

@keyframes fadeBackground {
    from { background-color: var(--cell-bg); }
    to { background-color: var(--cell-same-number-bg); }
}

.cell.error {
    color: var(--error-color);
    animation: shake 0.5s var(--transition-function);
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20%, 60% { transform: translateX(-5px); }
    40%, 80% { transform: translateX(5px); }
}

.cell .notes {
    position: absolute;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    width: 100%;
    height: 100%;
    font-size: var(--font-size-xs);
    color: #666;
    opacity: 0.8;
    transition: opacity var(--transition-speed-fast) var(--transition-function);
}

.cell:hover .notes {
    opacity: 1;
}

.dark-mode .cell .notes {
    color: #aaa;
}

.cell .notes span {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: var(--spacing-xs);
    transition: all var(--transition-speed-fast) var(--transition-function);
}

.cell .notes span:not(:empty) {
    animation: popIn 0.2s var(--transition-function-bounce);
}

@keyframes popIn {
    from { transform: scale(0); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

/* Add borders to separate 3x3 boxes */
.cell:nth-child(3n) {
    border-right: 2px solid var(--grid-border);
}

.cell:nth-child(9n) {
    border-right: none;
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom: 2px solid var(--grid-border);
}

.input-controls {
    width: 100%;
    margin-bottom: var(--spacing-lg);
}

.notes-toggle {
    margin-bottom: var(--spacing-md);
    text-align: center;
}

#notes-toggle-btn {
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--button-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: var(--font-size-sm);
    transition: all var(--transition-speed) var(--transition-function);
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

#notes-toggle-btn:hover {
    background-color: var(--button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

#notes-toggle-btn:active {
    transform: translateY(0);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

#notes-toggle-btn:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: 2px;
}

#notes-toggle-btn.active {
    background-color: var(--primary-button-bg);
    color: var(--primary-button-text);
    border-color: var(--primary-button-bg);
}

.number-pad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    grid-gap: var(--spacing-sm);
    width: 100%;
    animation: slideUp var(--transition-speed) var(--transition-function);
}

@keyframes slideUp {
    from { transform: translateY(10px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.number {
    padding: var(--spacing-md);
    font-size: var(--font-size-lg);
    background-color: var(--button-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    color: var(--text-color);
    transition: all var(--transition-speed-fast) var(--transition-function);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    font-weight: 500;
    position: relative;
    overflow: hidden;
}

.number::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle, rgba(255,255,255,0.3) 0%, rgba(255,255,255,0) 70%);
    transform: scale(0) translate(-50%, -50%);
    transform-origin: 0 0;
    opacity: 0;
    pointer-events: none;
    transition: transform 0.4s, opacity 0.3s;
}

.number:hover {
    background-color: var(--button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    transition: all var(--transition-speed-fast) var(--transition-function-ease-out);
}

.number:active {
    transform: translateY(0);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
    transition: all 0.1s var(--transition-function-sharp);
}

.number:active::after {
    transform: scale(3) translate(-50%, -50%);
    opacity: 1;
    transition: transform 0s, opacity 0.2s var(--transition-function-ease-out);
}

.number:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: 2px;
}

.number:last-child {
    grid-column: span 5;
    background-color: var(--button-hover-bg);
    font-size: var(--font-size-md);
}

.controls {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin-bottom: var(--spacing-lg);
    gap: var(--spacing-md);
}

.controls button {
    padding: var(--spacing-md);
    background-color: var(--primary-button-bg);
    color: var(--primary-button-text);
    border: none;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: var(--font-size-md);
    transition: all var(--transition-speed) var(--transition-function-ease-out);
    flex: 1;
    font-weight: 500;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: relative;
    overflow: hidden;
}

.controls button::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to bottom, rgba(255,255,255,0.1) 0%, rgba(255,255,255,0) 100%);
    opacity: 0;
    transition: opacity var(--transition-speed-fast) var(--transition-function-ease-out);
}

.controls button:hover::before {
    opacity: 1;
}

.controls button::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 5px;
    height: 5px;
    background: rgba(255, 255, 255, 0.5);
    opacity: 0;
    border-radius: 100%;
    transform: scale(1, 1) translate(-50%);
    transform-origin: 50% 50%;
}

.controls button:hover {
    background-color: var(--primary-button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

.controls button:active {
    transform: translateY(0);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
}

.controls button:focus {
    outline: 2px solid var(--primary-button-text);
    outline-offset: 2px;
}

.controls button:active::after {
    animation: ripple 1s ease-out;
}

@keyframes ripple {
    0% {
        transform: scale(0, 0);
        opacity: 0.5;
    }
    100% {
        transform: scale(20, 20);
        opacity: 0;
    }
}

.message {
    padding: var(--spacing-md);
    margin-top: var(--spacing-md);
    border-radius: var(--border-radius-sm);
    text-align: center;
    width: 100%;
    transition: all var(--transition-speed) var(--transition-function);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    font-weight: 500;
    opacity: 0;
    transform: translateY(-10px);
    height: 0;
    overflow: hidden;
    padding-top: 0;
    padding-bottom: 0;
    margin-top: 0;
}

.message:not(:empty) {
    opacity: 1;
    transform: translateY(0);
    height: auto;
    padding: var(--spacing-md);
    margin-top: var(--spacing-md);
    animation: slideDown var(--transition-speed) var(--transition-function-ease-out);
    position: relative;
}

.message:not(:empty)::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: currentColor;
    animation: progressBar 3s var(--transition-function-ease-in) forwards;
}

@keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes progressBar {
    from { width: 0; }
    to { width: 100%; }
}

.message.success {
    background-color: var(--success-bg);
    color: var(--success-text);
    border-left: 4px solid #28a745;
}

.message.error {
    background-color: var(--error-bg);
    color: var(--error-text);
    border-left: 4px solid #dc3545;
}

.stats-and-scores {
    width: 100%;
    margin-top: var(--spacing-xl);
    border-top: 1px solid var(--border-color);
    padding-top: var(--spacing-lg);
    animation: fadeIn var(--transition-speed-slow) var(--transition-function);
    animation-delay: 0.3s;
    animation-fill-mode: both;
}

.section-tabs {
    display: flex;
    justify-content: center;
    margin-bottom: var(--spacing-md);
    gap: var(--spacing-md);
}

.section-tab {
    padding: var(--spacing-sm) var(--spacing-lg);
    background-color: var(--button-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-speed) var(--transition-function);
    font-size: var(--font-size-md);
    font-weight: 500;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.section-tab:hover {
    background-color: var(--button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.section-tab:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: 2px;
}

.section-tab.active {
    background-color: var(--primary-button-bg);
    color: var(--primary-button-text);
    border-color: var(--primary-button-bg);
}

.tab-content {
    width: 100%;
}

.panel {
    display: none;
    animation: fadeIn var(--transition-speed) var(--transition-function);
}

.panel.active {
    display: block;
}

.stats-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.stat-card {
    background-color: var(--cell-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    text-align: center;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: transform var(--transition-speed) var(--transition-function);
}

.stat-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.stat-title {
    font-size: var(--font-size-sm);
    color: var(--text-color);
    opacity: 0.8;
    margin-bottom: var(--spacing-xs);
}

.stat-value {
    font-size: var(--font-size-xl);
    font-weight: bold;
    color: var(--primary-button-bg);
}

.stats-chart {
    margin-top: var(--spacing-lg);
}

.stats-chart h3 {
    text-align: center;
    margin-bottom: var(--spacing-md);
    font-size: var(--font-size-md);
    color: var(--text-color);
}

.chart-container {
    display: flex;
    justify-content: space-around;
    align-items: flex-end;
    height: 200px;
    padding: var(--spacing-md);
    background-color: var(--cell-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
}

.chart-bar {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 60px;
    height: 100%;
}

.bar-fill {
    width: 100%;
    background-color: var(--primary-button-bg);
    border-radius: var(--border-radius-sm) var(--border-radius-sm) 0 0;
    transition: height 1s var(--transition-function-ease-out);
}

.bar-label {
    margin-top: var(--spacing-xs);
    font-size: var(--font-size-xs);
    color: var(--text-color);
}

.score-tabs {
    display: flex;
    justify-content: center;
    margin-bottom: var(--spacing-md);
    gap: var(--spacing-sm);
}

.score-tab {
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--button-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-speed) var(--transition-function);
    font-size: var(--font-size-sm);
    font-weight: 500;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: relative;
    overflow: hidden;
}

.score-tab::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to bottom, rgba(255,255,255,0.2) 0%, rgba(255,255,255,0) 100%);
    opacity: 0;
    transition: opacity var(--transition-speed-fast) var(--transition-function);
}

.score-tab:hover {
    background-color: var(--button-hover-bg);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.score-tab:hover::after {
    opacity: 1;
}

.score-tab:focus {
    outline: 2px solid var(--primary-button-bg);
    outline-offset: 2px;
}

.score-tab.active {
    background-color: var(--primary-button-bg);
    color: var(--primary-button-text);
    border-color: var(--primary-button-bg);
    animation: tabActivate 0.3s var(--transition-function-bounce);
    position: relative;
}

.score-tab.active::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 50%;
    transform: translateX(-50%);
    width: 0;
    height: 0;
    border-left: 5px solid transparent;
    border-right: 5px solid transparent;
    border-top: 5px solid var(--primary-button-bg);
    animation: fadeIn 0.3s var(--transition-function-ease-out) forwards;
}

@keyframes tabActivate {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

.score-list {
    background-color: var(--cell-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    max-height: 250px;
    overflow-y: auto;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
    scrollbar-width: thin;
    scrollbar-color: var(--border-color) transparent;
    transition: all var(--transition-speed) var(--transition-function);
}

.score-list::-webkit-scrollbar {
    width: 8px;
}

.score-list::-webkit-scrollbar-track {
    background: transparent;
}

.score-list::-webkit-scrollbar-thumb {
    background-color: var(--border-color);
    border-radius: 20px;
    border: 2px solid var(--cell-bg);
}

.score-item {
    display: flex;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition-speed-fast) var(--transition-function-ease-out);
    animation: slideInRight 0.3s var(--transition-function-ease-out);
    animation-fill-mode: both;
    position: relative;
    overflow: hidden;
}

.score-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 3px;
    height: 100%;
    background-color: var(--primary-button-bg);
    transform: translateX(-100%);
    transition: transform var(--transition-speed-fast) var(--transition-function-ease-out);
}

@keyframes slideInRight {
    from { transform: translateX(-10px); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

.score-item:nth-child(1) { animation-delay: 0.05s; }
.score-item:nth-child(2) { animation-delay: 0.1s; }
.score-item:nth-child(3) { animation-delay: 0.15s; }
.score-item:nth-child(4) { animation-delay: 0.2s; }
.score-item:nth-child(5) { animation-delay: 0.25s; }

.score-item:hover {
    background-color: rgba(0, 0, 0, 0.02);
    transform: translateX(2px);
}

.score-item:hover::before {
    transform: translateX(0);
}

.score-item:last-child {
    border-bottom: none;
}

.no-scores {
    text-align: center;
    padding: var(--spacing-lg);
    color: var(--text-color);
    opacity: 0.7;
    font-style: italic;
    animation: fadeIn 1s var(--transition-function);
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideIn {
    from { transform: translateY(20px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

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

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-10px); }
    60% { transform: translateY(-5px); }
}

@keyframes flash {
    0%, 50%, 100% { opacity: 1; }
    25%, 75% { opacity: 0.5; }
}

.fade-in {
    animation: fadeIn 0.5s var(--transition-function);
}

.slide-in {
    animation: slideIn 0.5s var(--transition-function);
}

.rotate {
    animation: rotate 1s var(--transition-function) infinite;
}

.bounce {
    animation: bounce 1s var(--transition-function);
}

.flash {
    animation: flash 1s var(--transition-function);
}

/* Responsive Design */
@media (min-width: 1200px) {
    .container {
        max-width: var(--container-width-lg);
    }

    .game-board {
        max-width: var(--game-board-size-xl);
    }
}

@media (max-width: 992px) {
    html {
        font-size: 16px;
    }

    .container {
        max-width: var(--container-width-md);
        padding: var(--spacing-md);
    }

    .game-board {
        max-width: var(--game-board-size-lg);
    }
}

@media (max-width: 768px) {
    html {
        font-size: 15px;
    }

    .container {
        max-width: 95%;
        padding: var(--spacing-md);
    }

    .game-board {
        max-width: var(--game-board-size-md);
    }

    .game-options {
        justify-content: center;
        gap: var(--spacing-md);
    }
}

@media (max-width: 600px) {
    html {
        font-size: 14px;
    }

    .container {
        max-width: 100%;
        padding: var(--spacing-md) var(--spacing-sm);
        border-radius: 0;
    }

    .game-board {
        max-width: var(--game-board-size-sm);
    }

    .game-options {
        flex-direction: column;
        align-items: center;
        gap: var(--spacing-sm);
    }

    .timer, .difficulty, .theme-toggle, .sound-toggle {
        margin-bottom: var(--spacing-sm);
    }

    .controls {
        flex-direction: column;
        gap: var(--spacing-sm);
    }

    .controls button {
        width: 100%;
    }

    .number-pad {
        grid-template-columns: repeat(3, 1fr);
        gap: var(--spacing-xs);
    }

    .number {
        padding: var(--spacing-sm);
    }

    .number:last-child {
        grid-column: span 3;
    }

    .score-tabs {
        flex-wrap: wrap;
        gap: var(--spacing-xs);
    }

    .score-tab {
        font-size: var(--font-size-xs);
        padding: var(--spacing-xs) var(--spacing-sm);
    }
}

@media (max-width: 400px) {
    html {
        font-size: 12px;
    }

    body {
        padding: 0;
    }

    .container {
        padding: var(--spacing-sm);
        border-radius: 0;
        box-shadow: none;
    }

    .game-board {
        max-width: 100%;
    }

    h1 {
        font-size: var(--font-size-lg);
        margin-bottom: var(--spacing-sm);
    }

    .cell .notes {
        font-size: 0.6rem;
    }

    .high-scores {
        margin-top: var(--spacing-md);
        padding-top: var(--spacing-md);
    }
}

/* Portrait orientation on mobile */
@media (max-height: 600px) and (orientation: landscape) {
    .container {
        padding: var(--spacing-sm);
    }

    h1 {
        font-size: var(--font-size-lg);
        margin-bottom: var(--spacing-sm);
    }

    .game-board {
        max-width: 80vh;
        max-height: 80vh;
    }

    .high-scores {
        display: none;
    }
}

/* Accessibility - High Contrast Mode */
@media (forced-colors: active) {
    :root {
        --primary-button-bg: ButtonText;
        --primary-button-text: ButtonFace;
        --button-bg: Canvas;
        --button-hover-bg: CanvasText;
        --text-color: CanvasText;
        --border-color: CanvasText;
    }

    .cell:focus, .number:focus, .controls button:focus, #notes-toggle-btn:focus, .score-tab:focus {
        outline: 2px solid CanvasText;
    }
}