@mixin big-screen {
  @media (max-width: 1199px) and (min-width: 990px) {
    @content;
  }
}
@mixin medium-screen {
  @media screen and (max-width: 991px) {
    
    @content;
  }
}
@mixin small-screen {
  @media screen and (max-width: 768px) {
    @content;
  }
}
@mixin ex-small-screen {
  @media screen and (max-width: 498px) {
    @content;
  }
}