CODE EXAMPLE FOR CSS

responsive gradient background css

body {
  background-color: red;
}
#grad1 {
  height: 100px;
  width: 100%;
  background: linear-gradient(to bottom right, rgba(255, 255, 255, 0) 49.9%, rgba(255, 255, 255, 1) 50.1%);
}

<div id="grad1"></div>