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

body {
    background: linear-gradient(135deg, #1a1a1a 0%, #0a0a0a 100%);
    color: #ffffff;
    font-family: 'Arial', sans-serif;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    text-align: center;
    background: rgba(0, 0, 0, 0.5);
    border-radius: 20px;
    padding: 40px;
    box-shadow: 0 0 30px rgba(0, 255, 255, 0.1);
    backdrop-filter: blur(10px);
}

header {
    margin-bottom: 30px;
}

h1 {
    font-size: 3rem;
    margin-bottom: 20px;
    background: linear-gradient(45deg, #00ffff, #ff00ff);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    position: relative;
}

h1::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 100px;
    height: 3px;
    background: linear-gradient(90deg, #00ffff, #ff00ff);
    border-radius: 3px;
}

.game-info {
    margin: 30px 0;
    font-size: 1.4rem;
    color: #fff;
    text-shadow: 0 0 10px rgba(255, 255, 255, 0.5);
}

#reset-button {
    padding: 12px 25px;
    margin: 15px;
    font-size: 1.1rem;
    font-weight: bold;
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #fff;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 0 15px rgba(255, 0, 255, 0.3);
}

#reset-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 20px rgba(255, 0, 255, 0.5);
}

.game-board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    margin: 30px auto;
    max-width: 400px;
    background: rgba(34, 34, 34, 0.5);
    padding: 15px;
    border-radius: 15px;
    box-shadow: 0 0 30px rgba(0, 255, 255, 0.2);
}

.cell {
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    aspect-ratio: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 3.5rem;
    font-weight: bold;
    cursor: pointer;
    border-radius: 10px;
    transition: all 0.3s ease;
    user-select: none;
    box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.3);
}

.cell:hover:empty {
    background: linear-gradient(145deg, #2a2a2a, #1e1e1e);
    box-shadow: 0 0 15px rgba(0, 255, 255, 0.3);
}

.cell.x {
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #00ffff;
    text-shadow: 0 0 10px #00ffff;
}

.cell.o {
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #ff00ff;
    text-shadow: 0 0 10px #ff00ff;
}

.back-button {
    display: inline-block;
    margin-top: 30px;
    padding: 12px 25px;
    font-size: 1.1rem;
    font-weight: bold;
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #fff;
    text-decoration: none;
    border-radius: 10px;
    transition: all 0.3s ease;
    box-shadow: 0 0 15px rgba(0, 255, 0, 0.3);
}

.back-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 20px rgba(0, 255, 0, 0.5);
}

@keyframes winPulse {
    0% {
        transform: scale(1);
        opacity: 1;
    }
    50% {
        transform: scale(1.1);
        opacity: 0.8;
    }
    100% {
        transform: scale(1);
        opacity: 1;
    }
}

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

.cell.winner {
    animation: winPulse 1s ease-in-out infinite;
    box-shadow: 0 0 30px rgba(255, 215, 0, 0.6);
    background: linear-gradient(145deg, #2a2a2a, #1e1e1e);
    border: 2px solid gold;
}

.winner-text {
    animation: celebration 0.5s ease-in-out;
    font-size: 1.8rem;
    font-weight: bold;
    background: linear-gradient(45deg, gold, #ffd700);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 0 10px rgba(255, 215, 0, 0.5);
    margin: 20px 0;
}

.confetti {
    position: fixed;
    width: 10px;
    height: 10px;
    background-color: #f00;
    clip-path: polygon(50% 0%, 90% 20%, 100% 60%, 75% 100%, 25% 100%, 0% 60%, 10% 20%);
    animation: fall linear forwards;
}

@keyframes fall {
    to {
        transform: translateY(100vh) rotate(360deg);
    }
}

.hidden {
    display: none !important;
}

.mode-selection,
.difficulty-selection {
    text-align: center;
    margin: 30px 0;
}

h2 {
    font-size: 2rem;
    margin-bottom: 30px;
    background: linear-gradient(45deg, #00ffff, #ff00ff);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: 0 0 10px rgba(255, 255, 255, 0.1);
}

.mode-button,
.difficulty-button {
    display: block;
    width: 80%;
    max-width: 300px;
    margin: 15px auto;
    padding: 15px 30px;
    font-size: 1.2rem;
    font-weight: bold;
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #fff;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
}

.mode-button:hover,
.difficulty-button:hover {
    transform: translateY(-3px);
    box-shadow: 0 0 20px rgba(0, 255, 255, 0.3);
}

.mode-button[data-mode="2player"]:hover {
    box-shadow: 0 0 20px rgba(255, 0, 255, 0.3);
}

.mode-button[data-mode="ai"]:hover {
    box-shadow: 0 0 20px rgba(0, 255, 0, 0.3);
}

.difficulty-button[data-difficulty="easy"]:hover {
    box-shadow: 0 0 20px rgba(0, 255, 255, 0.3);
}

.difficulty-button[data-difficulty="medium"]:hover {
    box-shadow: 0 0 20px rgba(255, 165, 0, 0.3);
}

.difficulty-button[data-difficulty="hard"]:hover {
    box-shadow: 0 0 20px rgba(255, 0, 0, 0.3);
}

.game-controls {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin: 15px 0;
}

#reset-button,
#change-mode,
#back-to-mode {
    padding: 12px 25px;
    font-size: 1.1rem;
    font-weight: bold;
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #fff;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
}

#reset-button:hover,
#change-mode:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 20px rgba(255, 0, 255, 0.3);
}

.menu-button {
    display: inline-block;
    margin-top: 30px;
    padding: 12px 25px;
    font-size: 1.1rem;
    font-weight: bold;
    background: linear-gradient(145deg, #1e1e1e, #2a2a2a);
    color: #fff;
    text-decoration: none;
    border-radius: 10px;
    transition: all 0.3s ease;
    box-shadow: 0 0 15px rgba(0, 255, 0, 0.3);
}

.menu-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 0 20px rgba(0, 255, 0, 0.5);
}

@media (max-width: 500px) {
    .container {
        padding: 20px;
    }

    h1 {
        font-size: 2rem;
    }

    .game-info {
        font-size: 1.2rem;
    }

    .game-board {
        max-width: 300px;
        gap: 8px;
        padding: 10px;
    }
    
    .cell {
        font-size: 2.5rem;
    }

    #reset-button,
    .back-button {
        padding: 10px 20px;
        font-size: 1rem;
    }
}