.sound-btn {
    position: fixed;
    bottom: 16px;
    right: 16px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: none;
    background: #0d6efd; /* آبی */
    color: #fff;
    font-size: 18px;
    cursor: pointer;
    z-index: 9999;
    box-shadow: 0 4px 12px rgba(0,0,0,.25);
    transition: all .3s ease;
}