style.css

body {
  background-color: #eee;
  color: #444;
  font-family: -apple-system, helvetica;
  font-size: 1.25rem;
}

main,
header {
  margin-left: auto;
  margin-right: auto;
  max-width: 50rem;
  text-align: center;
}

h1 {
  color: #ccc;
  font-weight: normal;
  font-size: 2rem;
}

h2 {
  font-size: 4rem;
  color: #444;
}

body {
  padding-top: 4rem;
  padding-bottom: 4rem;
}

html {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100%;
  padding: 1rem;
  box-sizing: border-box;
}

input[type=button] {
  font-size: inherit;
  padding: 1rem 2rem;
  -webkit-appearance: button; /* for input */
    -webkit-user-select: none; /* for button */
       -moz-user-select: none;
        -ms-user-select: none;
        border-radius: 0.5rem;
        box-shadow: none;
        -webkit-box-shadow: none;
        border: none;
        background-color: #ccc;
        color: #fff;
        cursor: pointer;
}

input[type=button]:hover,
input[type=button]:active {
  background-color: #444;
}