.parent {
    display: flex;
    justify-content: center;
    align-items: center;
}

button {
    font-size: .825em;
    text-decoration: none;
    font-weight: 700;
    padding: .35em 1em;
    width: 6em;
    background-color: #eaeef1;
    background-image: linear-gradient(rgba(0,0,0,0), rgba(0,0,0,.1));
    border-radius: 3px;
    color: rgba(0,0,0,.6);
    text-shadow: 0 1px 1px rgba(255,255,255,.7);
    box-shadow: 0 0 0 1px rgba(0,0,0,.2), 0 1px 2px rgba(0,0,0,.2), inset 0 1px 2px rgba(255,255,255,.7);
}

button:hover, button.hover {
    background-color: #fff;
}

button:active, button.active {
    background-color: #d0d3d6;
    background-image: linear-gradient(rgba(0,0,0,.1), rgba(0,0,0,0));
    box-shadow: inset 0 0 2px rgba(0,0,0,.2), inset 0 2px 5px rgba(0,0,0,.2), 0 1px rgba(255,255,255,.2);
}

.b {
    width:65px; height:65px;font-size: 25px;
}

.slider {
    -webkit-appearance: none;
    width: 100%;
    height: 15px;
    border-radius: 5px;   
    background: #d3d3d3;
    outline: none;
    opacity: 0.7;
    -webkit-transition: .2s;
    transition: opacity .2s;
  }
  
  .slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 25px;
    height: 25px;
    border-radius: 50%; 
    background: #4CAF50;
    cursor: pointer;
  }
  
  .slider::-moz-range-thumb {
    width: 25px;
    height: 25px;
    border-radius: 50%;
    background: #4CAF50;
    cursor: pointer;
  }