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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #1a1a1a;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 16px;
}

.header {
    background: rgba(255,255,255,0.95);
    padding: 20px;
    border-radius: 12px;
    margin-bottom: 16px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    backdrop-filter: blur(10px);
    text-align: center;
}

.header h1 {
    font-size: 32px;
    font-weight: 800;
    margin-bottom: 20px;
    background: linear-gradient(45deg, #667eea, #764ba2);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.game-stats {
    display: flex;
    justify-content: center;
    gap: 32px;
    flex-wrap: wrap;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    padding: 12px;
    background: rgba(255,255,255,0.5);
    border-radius: 12px;
    min-width: 80px;
}

.stat-icon {
    font-size: 24px;
}

.stat-value {
    font-size: 24px;
    font-weight: 700;
    color: #667eea;
}

.stat-label {
    font-size: 11px;
    color: #666;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.game-area {
    background: rgba(255,255,255,0.95);
    border-radius: 12px;
    padding: 24px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.1);
    backdrop-filter: blur(10px);
    margin-bottom: 16px;
}

.difficulty-selector {
    text-align: center;
}

.difficulty-selector h2 {
    font-size: 24px;
    font-weight: 700;
    margin-bottom: 24px;
    color: #667eea;
}

.difficulty-buttons {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
    max-width: 600px;
    margin: 0 auto;
}

.difficulty-btn {
    background: rgba(255,255,255,0.8);
    border: 2px solid #e0e0e0;
    border-radius: 12px;
    padding: 20px;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.difficulty-btn:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15);
    border-color: #667eea;
    background: rgba(102, 126, 234, 0.05);
}

.difficulty-icon {
    font-size: 32px;
}

.difficulty-name {
    font-size: 18px;
    font-weight: 600;
    color: #1a1a1a;
}

.difficulty-desc {
    font-size: 12px;
    color: #666;
}

.game-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    padding-bottom: 16px;
    border-bottom: 1px solid #e0e0e0;
}

.current-difficulty {
    display: flex;
    align-items: center;
    gap: 12px;
}

.current-difficulty span {
    font-weight: 600;
    color: #667eea;
}

.change-difficulty-btn {
    background: rgba(102, 126, 234, 0.1);
    border: 1px solid #667eea;
    border-radius: 6px;
    padding: 4px 8px;
    font-size: 12px;
    cursor: pointer;
    color: #667eea;
    transition: all 0.2s;
}

.change-difficulty-btn:hover {
    background: #667eea;
    color: white;
}

.turn-indicator {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 18px;
    font-weight: 600;
}

.thinking-dots {
    display: flex;
    gap: 4px;
}

.thinking-dots span {
    width: 6px;
    height: 6px;
    background: #667eea;
    border-radius: 50%;
    animation: thinking 1.4s ease-in-out infinite both;
}

.thinking-dots span:nth-child(1) { animation-delay: -0.32s; }
.thinking-dots span:nth-child(2) { animation-delay: -0.16s; }

@keyframes thinking {
    0%, 80%, 100% { transform: scale(0); }
    40% { transform: scale(1); }
}

.game-board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    gap: 8px;
    max-width: 300px;
    margin: 0 auto 24px auto;
    aspect-ratio: 1;
    background: #e0e0e0;
    border-radius: 12px;
    padding: 8px;
}

.cell {
    background: white;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 48px;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.cell:hover:not(.x):not(.o) {
    background: rgba(102, 126, 234, 0.1);
    transform: scale(1.05);
}

.cell.x {
    color: #ef4444;
    background: rgba(239, 68, 68, 0.1);
}

.cell.o {
    color: #10b981;
    background: rgba(16, 185, 129, 0.1);
}

.cell.winning {
    animation: winningCell 0.6s ease-in-out;
    background: linear-gradient(45deg, #ffd700, #ffed4e) !important;
    color: #333 !important;
}

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

.cell.hint {
    animation: hintPulse 1s ease-in-out;
    background: rgba(255, 193, 7, 0.3) !important;
}

@keyframes hintPulse {
    0%, 100% { transform: scale(1); opacity: 1; }
    50% { transform: scale(1.1); opacity: 0.7; }
}

.cell-animation {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 48px;
    animation: cellPlace 0.3s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

@keyframes cellPlace {
    0% { transform: translate(-50%, -50%) scale(0) rotate(180deg); }
    100% { transform: translate(-50%, -50%) scale(1) rotate(0deg); }
}

.game-message {
    text-align: center;
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 24px;
    min-height: 24px;
    color: #667eea;
}

.game-controls {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.control-btn {
    background: rgba(255,255,255,0.8);
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    padding: 12px 16px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    gap: 6px;
}

.control-btn:hover:not(:disabled) {
    border-color: #667eea;
    background: rgba(102, 126, 234, 0.1);
    transform: translateY(-2px);
}

.control-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.restart-btn:hover {
    border-color: #10b981;
    background: rgba(16, 185, 129, 0.1);
}

.hint-btn:hover {
    border-color: #f59e0b;
    background: rgba(245, 158, 11, 0.1);
}

.undo-btn:hover {
    border-color: #8b5cf6;
    background: rgba(139, 92, 246, 0.1);
}

.achievements-panel {
    background: rgba(255,255,255,0.95);
    border-radius: 12px;
    padding: 16px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    backdrop-filter: blur(10px);
}

.achievements-panel h3 {
    margin-bottom: 12px;
    font-size: 16px;
    font-weight: 600;
    text-align: center;
}

.achievements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(60px, 1fr));
    gap: 8px;
}

.achievement {
    aspect-ratio: 1;
    background: rgba(255,255,255,0.5);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    cursor: pointer;
    transition: all 0.2s;
    border: 2px solid transparent;
    position: relative;
}

.achievement.unlocked {
    background: linear-gradient(135deg, #ffd700 0%, #ffed4e 100%);
    border-color: #ffa500;
    animation: achievement-glow 2s ease-in-out infinite alternate;
}

@keyframes achievement-glow {
    from { box-shadow: 0 0 5px rgba(255, 215, 0, 0.5); }
    to { box-shadow: 0 0 15px rgba(255, 215, 0, 0.8); }
}

.achievement:hover {
    transform: scale(1.1);
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.8);
    z-index: 2000;
    justify-content: center;
    align-items: center;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: white;
    padding: 32px;
    border-radius: 16px;
    text-align: center;
    max-width: 400px;
    margin: 20px;
    box-shadow: 0 12px 40px rgba(0,0,0,0.3);
    position: relative;
    overflow: hidden;
}

.win-animation {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.confetti {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><circle cx="20" cy="20" r="2" fill="%23ffd700"/><circle cx="80" cy="30" r="2" fill="%23ff6b6b"/><circle cx="60" cy="70" r="2" fill="%234ecdc4"/><circle cx="30" cy="80" r="2" fill="%23ffe66d"/></svg>') repeat;
    animation: confetti-fall 3s linear infinite;
    opacity: 0.7;
}

@keyframes confetti-fall {
    0% { transform: translateY(-100%); }
    100% { transform: translateY(100vh); }
}

.win-content {
    position: relative;
    z-index: 1;
}

.win-icon {
    font-size: 64px;
    margin-bottom: 16px;
    animation: bounce 1s ease-in-out infinite alternate;
}

@keyframes bounce {
    0% { transform: translateY(0); }
    100% { transform: translateY(-10px); }
}

.win-content h2 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 12px;
}

.win-content p {
    font-size: 16px;
    margin-bottom: 24px;
    opacity: 0.9;
}

.win-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

.win-actions button {
    background: rgba(255,255,255,0.2);
    border: 2px solid rgba(255,255,255,0.3);
    color: white;
    padding: 12px 20px;
    border-radius: 25px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.win-actions button:hover {
    background: rgba(255,255,255,0.3);
    border-color: rgba(255,255,255,0.5);
    transform: scale(1.05);
}

.sound-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

.sound-toggle button {
    background: rgba(255,255,255,0.9);
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    font-size: 20px;
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    transition: all 0.2s;
}

.sound-toggle button:hover {
    transform: scale(1.1);
    box-shadow: 0 6px 20px rgba(0,0,0,0.2);
}

.sound-toggle button.muted {
    opacity: 0.5;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 12px;
    }
    
    .header {
        padding: 16px;
    }
    
    .header h1 {
        font-size: 24px;
    }
    
    .game-stats {
        gap: 16px;
    }
    
    .stat {
        min-width: 60px;
        padding: 8px;
    }
    
    .game-area {
        padding: 16px;
    }
    
    .difficulty-buttons {
        grid-template-columns: 1fr;
        gap: 12px;
    }
    
    .difficulty-btn {
        padding: 16px;
    }
    
    .game-board {
        max-width: 280px;
    }
    
    .cell {
        font-size: 36px;
    }
    
    .game-info {
        flex-direction: column;
        gap: 12px;
        text-align: center;
    }
    
    .game-controls {
        gap: 8px;
    }
    
    .control-btn {
        padding: 10px 12px;
        font-size: 12px;
    }
}

@media (max-width: 480px) {
    .game-board {
        max-width: 240px;
    }
    
    .cell {
        font-size: 28px;
    }
    
    .modal-content {
        margin: 10px;
        padding: 24px;
    }
}
/* Footer styles */
footer {
    text-align: center;
    padding: 20px;
    margin-top: 20px;
    border-top: 1px solid #e0e0e0;
    font-size: 14px;
}

footer a {
    color: #666;
    text-decoration: none;
    margin: 0 10px;
    transition: color 0.2s ease;
}

footer a:hover,
footer a:focus {
    color: #4CAF50;
    text-decoration: underline;
}