* {
  box-sizing: border-box;
}
body {
  padding: 0;
  margin: 0;
  background: #471db1;
}
form {
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
  padding: 15px;
  background: #FFF;
  border-radius: 20px;
  margin-top: 15px;
  box-shadow: 10px 10px 53px 8px rgba(0, 0, 0, 0.75);
  -webkit-box-shadow: 10px 10px 53px 8px rgba(0, 0, 0, 0.75);
  -moz-box-shadow: 10px 10px 53px 8px rgba(0, 0, 0, 0.75);
}
form h1 {
  margin: 0;
}
form label {
  display: block;
}
form input {
  width: 100%;
  margin-bottom: 10px;
  padding: 5px;
  border-radius: 5px;
  border: 1px #000 solid;
}
form button {
  margin-top: 10px;
}
.btn {
  padding: 12px 20px;
  font-size: 16px;
  border: none;
  border-radius: 5px;
  color: #000;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  transition: 0.3s;
  background-size: 200% 100%;
}
.btn:hover {
  background: #cacaca;
}
.btn.loading {
  display: block;
  width: 100%;
  color: transparent;
  pointer-events: none;
}
.btn.loading::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: repeating-linear-gradient(45deg, #000 0%, #000 10%, #fff 10%, #fff 20%);
  background-size: 1000px 50px;
  z-index: 0;
  transition: 0.3s;
  animation: zebraMove 4s linear infinite;
}
@keyframes zebraMove {
  from {
    background-position: 0 0;
  }
  to {
    background-position: 1000px 0px;
  }
}