body {
    font-family: sans-serif;
    background: #f0f4f8;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    text-align: center;
}
.screen { width: 90%; max-width: 400px; }
button {
    padding: 12px 20px;
    font-size: 16px;
    background: #007bff;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    margin: 5px;
}
input {
    padding: 10px;
    font-size: 16px;
    text-align: center;
    border: 2px solid #ccc;
    border-radius: 8px;
    width: 150px;
}
.error { color: red; font-weight: bold; }

/* Игровое поле */
.board {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    margin: 20px auto;
    width: 300px;
    height: 300px;
}
.cell {
    background: white;
    border-radius: 10px;
    font-size: 40px;
    font-weight: bold;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: background 0.2s;
}
.cell:active { background: #e2e8f0; }
.cell.x { color: #e53e3e; }
.cell.o { color: #3182ce; }