:root{
  --product-nav-height:74px;
  --product-nav-offset:var(--product-nav-height);
}

body.product-page{
  margin:0;
  position:relative;
  background:transparent;
}

body.product-page::before{
  content:"";
  position:fixed;
  top:var(--product-nav-offset);
  left:0;
  width:100%;
  height:calc(100vh - var(--product-nav-offset));
  background-image:var(--product-page-bg);
  background-position:center top;
  background-repeat:no-repeat;
  background-size:100% 100%;
  z-index:-2;
  transition:top .22s ease, height .22s ease;
}

body.product-page main,
body.product-page .apps-nav,
body.product-page .wos-nav{
  position:relative;
  z-index:1;
}

@media (max-width:780px){
  body.product-page::before{
    background-size:100% 100%;
  }
}

@media (max-width:640px){
  :root{
    --product-nav-height:64px;
  }
}