style.css

body {
  background-color: #5f5f5f;
  opacity: 1;
  background-image: radial-gradient(circle at center center, #000000, #5f5f5f), repeating-radial-gradient(circle at center center, #000000, #000000, 40px, transparent 80px, transparent 40px);
  background-blend-mode: multiply;
  margin: 0;
  padding: 0;
  font-family: Arial, sans-serif;
}

#container {
  background: rgb(2,0,36);
  background: linear-gradient(90deg, rgba(0,0,0,0.5) 0%, rgba(95,95,95,0.5) 69%, rgba(95,95,95,0.5) 100%);
  color: #fff;
  height: auto;
  width: 90%;
  max-width: 750px;
  border-radius: 10px;
  margin: 20px auto;
  text-align: center;
  padding: 20px;
}

.button {
appearance: button;
background-color: #000;
background-image: none;
border: 1px solid #000;
border-radius: 4px;
box-shadow: #fff 4px 4px 0 0,#000 4px 4px 0 1px;
box-sizing: border-box;
color: #fff;
cursor: pointer;
display: inline-block;
font-family: ITCAvantGardeStd-Bk, Arial, sans-serif;
font-size: 18px;
font-weight: 400;
line-height: 20px;
margin: 10px 5px;
overflow: visible;
padding: 12px 20px;
text-align: center;
text-transform: none;
touch-action: manipulation;
user-select: none;
-webkit-user-select: none;
vertical-align: middle;
white-space: nowrap;
}

.button:focus {
text-decoration: none;
}

.button:hover {
text-decoration: none;
}

.button:active {
box-shadow: rgba(0, 0, 0, .125) 0 3px 5px inset;
outline: 0;
}

.button:not([disabled]):active {
box-shadow: #fff 2px 2px 0 0, #000 2px 2px 0 1px;
transform: translate(2px, 2px);
}

@media (min-width: 768px) {
.button {
  padding: 12px 50px;
}
}