main {
   width: 100vw;
   min-width: 300px;
   margin: 0 auto;
   font-size: 20px;
}

div {
   background-color: lightgray;
   margin-bottom: 1em;
}

button, label, input {
   display: block;
   margin: 0.5rem auto
}

h1, div, button, input, label {
   text-align: center;
}

#change-due {
   background-color: white;
   border: 1px solid black;
}