* {
  box-sizing: border-box;
}
body {
  margin:0;
}
header {
  height:100vh;
  position: relative;
}
header::before {
  content:'';
  position: absolute;
  width: 100%;
  height: 100%;
  background:linear-gradient(309deg, rgba(103,11,62,0) 9%, rgba(9,238,151,0.7511379551820728) 100%);
}
video {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
img {
  position: absolute;
  top:50%;
  left:50%;
  transform:translate(-50%,-50%);
}