body {
    display: flex; justify-content: center; align-items: center;
    height: 100vh; margin: 0;
    background-color: #2b1d0e; /* より深い茶色 */
    background-image: repeating-linear-gradient(45deg, #2b1d0e 0px, #2b1d0e 10px, #362512 10px, #362512 20px);
    font-family: 'Helvetica Neue', Arial, sans-serif;
}
.container { 
    text-align: center;
    background-color: rgba(0, 0, 0, 0.6);
    padding: 30px; border-radius: 15px;
    box-shadow: 0 0 30px rgba(0,0,0,0.7);
}
.board {
    display: grid; grid-template-columns: repeat(10, 35px);
    grid-template-rows: repeat(10, 35px); gap: 2px;
    background-color: #5d4037;
    border: 6px solid #5d4037; margin: 20px auto;
}
.cell {
    width: 35px; height: 35px; background-color: #fdf5e6;
    display: flex; justify-content: center; align-items: center;
    font-size: 1.8rem; font-weight: 900;
}
.cell.none { background-color: transparent; border: none; }
.player { color: #007bff; text-shadow: 1px 1px 2px rgba(0,0,0,0.3); }
.circle { color: #a1887f; text-shadow: 1px 1px 2px rgba(0,0,0,0.3); }
.cross { color: #3e2723; text-shadow: 1px 1px 2px rgba(0,0,0,0.3); }
.status { font-weight: bold; font-size: 1.4rem; color: #fff; margin-bottom: 10px; }
.big-btn { padding: 20px 40px; font-size: 1.5rem; cursor: pointer; background-color: #d2b48c; color: #3e2723; border: none; border-radius: 10px; font-weight: bold; }
.reset-btn { padding: 10px 20px; cursor: pointer; background-color: #8d6e63; color: white; border: none; border-radius: 5px; }