style.css

body
{      
    height: 100%;                 
    margin: 0px;
    padding: 0px;
    
    background: #313853;
    
    font-family: Tahoma,Verdana,Segoe,sans-serif; 
    color: #444;
}

div
{
    box-sizing: border-box;
}

h3
{
    font-weight: normal;
}

.main
{
    width: 70%;
    height: 100%;
    margin-left: 15%;
    margin-right: 15%;
    padding: 32px;
    
    min-width: 400px;
    min-height: 740px;

    background: #eee;
}

input[type=number]
{
    height: 40px;
    padding: 12px;
    
    font-size: 24px;
    text-align: center;
    
    border: 0px;
}

input::-webkit-outer-spin-button, input::-webkit-inner-spin-button
{
  -webkit-appearance: none;
  margin: 0;
}

input[type=number] 
{
  -moz-appearance: textfield;
}

#time
{
    font-weight: bold;
}

@media screen and ( max-width: 800px )
{

  .main
  {
      width: 100% !important;
      margin-left: 0%;
      margin-right: 0%;
  }

}