Hi there,
You could try something like this:
.offside--left.is-open {
-webkit-transform: translate3d(350px,0,0);
-moz-transform: translate3d(350px,0,0);
-ms-transform: translate3d(350px,0,0);
-o-transform: translate3d(350px,0,0);
transform: translate3d(350px,0,0);
}
.main-navigation.offside {
width: 350px;
}
.main-navigation.offside.is-open {
margin: 50px 40px;
}
.offside, .offside--left {
left: -350px;
}
.offside-js--is-left.slide-opened .slideout-overlay button.slideout-exit {
left: 40px;
top: 0;
}
Let me know 🙂