Hamburger Menu Customisation Desktop

Hi there, 

Wanting some help on creating a custom hamburger menu for desktop, that only takes up half of the screen horizontally (see picture attached). With the logo and menu items positioned as pictured also.

Site url is https://primrose-whale-2sxx.squarespace.com/
pw: 1234

Thank you!

You can use this code to Website Tools > Custom CSS

div.header-menu {
    bottom: unset !important;
    height: 70vh !important;
    transform: translateY(-100%);
    transition: all 0.3s ease;
}
body.header--menu-open div.header-menu {
    transform: translateY(0);
    transition: all 0.3s ease;
}
.header-menu-nav-wrapper * {
    text-align: center;
}