body {
    background: #181c24;
    color: #f5f6fa;
    min-height: 100vh;
    margin: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Segoe UI', 'Roboto', Arial, sans-serif;
}
.container {
    background: #23283a;
    padding: 48px 32px 40px 32px;
    border-radius: 18px;
    box-shadow: 0 6px 32px rgba(0,0,0,0.25);
    display: flex;
    flex-direction: column;
    align-items: center;
    min-width: 340px;
    max-width: 98vw;
}
h1 {
    margin-bottom: 36px;
    font-size: 2.2rem;
    font-weight: 700;
    letter-spacing: 1px;
    text-align: center;
}
.button-group {
    display: flex;
    flex-direction: column;
    gap: 22px;
    width: 100%;
    margin-bottom: 10px;
}
.main-btn {
    padding: 18px 0;
    font-size: 1.25rem;
    font-weight: 600;
    border: none;
    border-radius: 12px;
    background: #2e344d;
    color: #f5f6fa;
    cursor: pointer;
    transition: background 0.2s, color 0.2s, transform 0.15s;
    box-shadow: 0 2px 8px rgba(0,0,0,0.10);
}
.main-btn:hover {
    background: #4b5cff;
    color: #fff;
    transform: translateY(-2px) scale(1.03);
}
.difficulty-group {
    display: flex;
    flex-direction: column;
    gap: 18px;
    width: 100%;
    margin-top: 18px;
}
.difficulty-btn {
    padding: 14px 0;
    font-size: 1.1rem;
    font-weight: 500;
    border: none;
    border-radius: 10px;
    background: #23283a;
    color: #f5f6fa;
    cursor: pointer;
    transition: background 0.2s, color 0.2s, transform 0.15s;
}
.difficulty-btn:hover {
    background: #4b5cff;
    color: #fff;
    transform: translateY(-2px) scale(1.03);
}
.hidden {
    display: none !important;
}
#board {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    grid-template-rows: repeat(8, 1fr);
    gap: 0.7vw;
    justify-content: center;
    background: #181c24;
    padding: 1.5vw;
    border-radius: 16px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.18);
    width: 45vw;
    max-width: 520px;
    min-width: 320px;
    aspect-ratio: 1 / 1;
}
.cell {
    width: 100%;
    height: 100%;
    background: #2e344d;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background 0.2s;
    position: relative;
}
.cell.disabled {
    cursor: default;
}
.move-dot {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    width: 28%;
    height: 28%;
    border-radius: 50%;
    background: rgba(120,180,255,0.45);
    pointer-events: none;
    z-index: 1;
}
.disk {
    display: block;
    border-radius: 50%;
    width: 70%;
    height: 70%;
    font-size: 2.7vw;
    min-font-size: 1.2rem;
    max-font-size: 3.2rem;
}
.disk.black {
    background: #222;
    box-shadow: 0 0 4px #000a;
}
.disk.white {
    background: #fff;
    box-shadow: 0 0 4px #000a;
}
#roomIdShow {
    font-weight: bold;
    font-size: 1.2rem;
    letter-spacing: 2px;
    background: #181c24;
    padding: 2px 8px;
    border-radius: 7px;
    margin: 0 4px;
}
@media (max-width: 700px) {
    #board {
        width: 96vw;
        min-width: 0;
        max-width: 98vw;
        padding: 2vw;
        gap: 1vw;
    }
    .container {
        min-width: 0;
        padding: 18px 2vw 18px 2vw;
    }
}
@media (max-width: 400px) {
    #board {
        padding: 1vw;
        gap: 0.5vw;
    }
}