.bgm-toggle {
    position: fixed;
    right: 18px;
    bottom: 18px;
    z-index: 10000;
    background: rgba(15, 23, 42, 0.85);
    color: #ffffff;
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 999px;
    padding: 10px 14px;
    font-size: 0.9rem;
    font-weight: 700;
    letter-spacing: 0.02em;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.35);
    cursor: pointer;
    transition: transform 0.15s ease, background-color 0.2s ease, border-color 0.2s ease;
}

.bgm-toggle:hover {
    transform: translateY(-1px);
    background: rgba(30, 41, 59, 0.9);
    border-color: rgba(255, 255, 255, 0.35);
}

.bgm-toggle.is-on {
    background: rgba(59, 130, 246, 0.9);
    border-color: rgba(59, 130, 246, 0.9);
}

.bgm-credit {
    position: fixed;
    right: 18px;
    bottom: 64px;
    z-index: 9999;
    background: rgba(15, 23, 42, 0.75);
    color: #e2e8f0;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 10px;
    padding: 6px 10px;
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.01em;
    max-width: 220px;
    text-align: right;
}

@media (max-width: 640px) {
    .bgm-toggle {
        right: 12px;
        bottom: 12px;
        padding: 8px 12px;
        font-size: 0.85rem;
    }

    .bgm-credit {
        right: 12px;
        bottom: 52px;
        max-width: 180px;
    }
}