.menu {
    @include animation-duration(0.3s);
    .slide-down     & { @include animation-name(slide_down);    }
    .slide-up       & { @include animation-name(slide_up);      }
    .slide-context  & { @include animation-name(slide_context); }
}

.slide {
    overflow: hidden;
}

.menu {
    @include animation-duration(0.3s);
}
.slide-down     .menu { @include animation-name(slide_down);    }
.slide-up       .menu { @include animation-name(slide_up);      }
.slide-context  .menu { @include animation-name(slide_context); }

.slide {
    overflow: hidden;
}

Move .slide-* .menu outside of .menu
Move .slide-* .menu outside of .menu

This is to prevent to use `&`,
which became problematic when I tried to do like this:

    .some-basic-class {
        @import _win98_menu_animation;
    }

then `&` is `.some-basic-class .menu`, not `.menu`.
