* {
  box-sizing: border-box;
}

body {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
  overflow: hidden;
  margin: 0;
}

.background {
  background: url(https://images.unsplash.com/photo-1602347671057-e2be757b37c6?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=667&q=80)
    no-repeat center center/cover;
  position: absolute;
  top: -20px;
  bottom: -20px;
  left: -20px;
  right: -20px;
  z-index: -1;
  filter: blur(20px);
}