#header { position: fixed!important; }
#header.moveup { animation: anime-up 0.5s forwards; }
@keyframes anime-up{
  from { opacity: 1; transform: translateY(0); }
  to { opacity: 0; transform: translateY(-100px); }
}
#header.movedown{ animation: anime-down 0.5s forwards; }
@keyframes anime-down{
  from { opacity: 0; transform: translateY(-100px); }
  to { opacity: 1; transform: translateY(0); }
}
.img-invert {filter: invert();}
.txt-invert {color: #000;}