.foo {
  flex: 1;
}
.bar {
  flex: 1 1;
}
.foz {
  flex: 1 1 0;
}
.baz {
  flex: 1 1 0px;
}

@custom-media --wide-window (min-width: 30em);

@media (--wide-window) {
  background: yellow;
}

.logo {
  backdrop-filter: blur(10px);
  background: yellow;
}

.button {
  -webkit-transition: background 200ms;
  -moz-transition: background 200ms;
  transition: background 200ms;
}