header.block-header {
  position: relative;
  background: linear-gradient(
    120deg,
    #1f1f1f,
    #2c2c2c,
    #242424
  );
  background-size: 300% 300%;
  animation: headerMetalFlow 14s ease infinite;

  box-shadow:
    inset 0 1px 0 rgba(255,255,255,0.08),
    inset 0 -2px 0 rgba(0,0,0,0.5),
    0 14px 40px rgba(0,0,0,0.4);

  border-radius: 0 0 18px 18px;
  overflow: hidden;
}
header.block-header::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(
    60deg,
    transparent,
    rgba(255,255,255,0.07),
    transparent
  );
  animation: headerLightSweep 7s linear infinite;
  pointer-events: none;
}
@keyframes headerMetalFlow {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

@keyframes headerLightSweep {
  0%   { transform: translateX(-120%); }
  100% { transform: translateX(120%); }
}