mixin navEntry(name, hasChildren)
    if (hasChildren === true)
        input(type='checkbox' id='nav_' + name).main-nav__child-trigger
    li.main-nav__entry
        if (hasChildren === true)
            label(for='nav_'+name).main-nav__child-trigger-helper
        a(href='#'+name).main-nav__link= name

body
    header.header
        .header__logo ✌
            span.header__logotext Awesome App!
    nav.main-nav
        input(type='checkbox').main-nav__burger#burger
        label(for='burger').main-nav__burger-helper
        ul.main-nav__list
            +navEntry('Lorem')
            +navEntry('Ipsum')
            +navEntry('Dolor', true)
            ul.main-nav__list.main-nav__list--is-sub
                label(for='nav_Dolor').main-nav__back
                +navEntry('Dolor Lorem')
                +navEntry('Dolor Dolor')
            +navEntry('Sit', true)
            ul.main-nav__list.main-nav__list--is-sub
                label(for='nav_Sit').main-nav__back
                +navEntry('Sit Lorem')
                +navEntry('Sit Ipsum')
                +navEntry('Sit Dolor')
            +navEntry('Amet')
    .content
        p Voluptates et placeat et et et vel itaque est. Quasi saepe excepturi ea alias cum fugiat hic. Eius et ratione nostrum esse. Voluptatibus nostrum odio quia sed repudiandae. Aut omnis voluptatem voluptatem temporibus et qui quia porro. Voluptas exercitationem molestiae expedita ea dicta voluptatum. Quo et officia ea repellendus. Dolorem et et aut consequuntur nesciunt corrupti quasi. Eos dolore non at.
        p Voluptates et placeat et et et vel itaque est. Quasi saepe excepturi ea alias cum fugiat hic. Eius et ratione nostrum esse. Voluptatibus nostrum odio quia sed repudiandae. Aut omnis voluptatem voluptatem temporibus et qui quia porro. Voluptas exercitationem molestiae expedita ea dicta voluptatum. Quo et officia ea repellendus. Dolorem et et aut consequuntur nesciunt corrupti quasi. Eos dolore non at.
        p Voluptates et placeat et et et vel itaque est. Quasi saepe excepturi ea alias cum fugiat hic. Eius et ratione nostrum esse. Voluptatibus nostrum odio quia sed repudiandae. Aut omnis voluptatem voluptatem temporibus et qui quia porro. Voluptas exercitationem molestiae expedita ea dicta voluptatum. Quo et officia ea repellendus. Dolorem et et aut consequuntur nesciunt corrupti quasi. Eos dolore non at.
        p Voluptates et placeat et et et vel itaque est. Quasi saepe excepturi ea alias cum fugiat hic. Eius et ratione nostrum esse. Voluptatibus nostrum odio quia sed repudiandae. Aut omnis voluptatem voluptatem temporibus et qui quia porro. Voluptas exercitationem molestiae expedita ea dicta voluptatum. Quo et officia ea repellendus. Dolorem et et aut consequuntur nesciunt corrupti quasi. Eos dolore non at.
        
        p full responsive demo 
          a(href='http://playground.iamschulz.de/skeleton/') here
        

@primary-color: #FF5300;
@text-color: #333;
@bg-color: #ddd;
@shadow-color: rgba(0, 0, 0, 0.5);

@break-m: 64.0225em; // 1025px

@z-header: 5000;
@z-nav: 4000;

@transition: 0.2s ease-out;

.container {
    max-width: 1440 / 16em;
    margin: auto;
}

* {
    --header-height: 60px;
}

body {
    margin: 0;
    padding: 0;
    background-color: @bg-color;
    font: 16px/1.5 sans-serif;
}

.header {
    &:extend(.container);
    position: sticky;
    top: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: var(--header-height);
    background-color: @primary-color;
    color: @bg-color;
    box-shadow: 0 0 10px 0 @shadow-color;
    z-index: @z-header;

    &__logo {
        display: flex;
        justify-content: center;
        align-items: center;
        font-size: 1.8em;
    }

    &__logotext {
        font-weight: 700;
        text-transform: uppercase;
    }
}

.main-nav {
    position: sticky;
    top: 0;
    right: 0;
    margin-top: calc(-1 ~"*" var(--header-height));
    z-index: @z-header;

    &__burger {
        display: none;
    }

    &__burger-helper {
        position: absolute;
        right: 0;
        display: flex;
        justify-content: center;
        align-items: center;
        width: var(--header-height);
        height: var(--header-height);
        font-size: 40px;
        z-index: @z-header;
        cursor: pointer;

        &::before {
            content: "";
            position: absolute;
            left: calc(-100vw ~"+" var(--header-height));
            top: var(--header-height);
            width: 100vw;
            height: calc(100vh ~"-" var(--header-height));
            background-color: @shadow-color;
            opacity: 0;
            pointer-events: none;
            transition: opacity @transition;
            z-index: @z-nav;

            .main-nav__burger:checked ~ & {
                opacity: 1;
                pointer-events: all;
            }
        }

        &::after {
            content: '🍔';
        }

        .main-nav__burger:checked + &::after {
            content: '❌';
        }
    }

    &__list {
        position: fixed;
        right: 0;
        top: var(--header-height);
        width: 250px;
        max-width: 80vw;
        height: 100vh;
        margin: 0;
        padding: 10px 0 0;
        background: darken(@primary-color, 5%);
        list-style: none;
        transform: translateX(100%);
        transition: transform @transition, box-shadow @transition;
        overflow: hidden;
        z-index: @z-header;

        &--is-sub {
            opacity: 0;
            transition: transform @transition, box-shadow @transition, opacity @transition;
        }

        .main-nav__burger:checked ~ & {
            box-shadow: 0 5px 10px 0 @shadow-color;
            opacity: 1;
            transform: translateX(0);
        }
    }

    &__entry {
        position: relative;
        padding: 5px 10px;

        .main-nav__child-trigger:checked + & {
            position: absolute;
            top: 10px;
            z-index: @z-nav + 2;
        }
    }

    &__link {
        display: flex;
        justify-content: flex-end;
        align-items: center;
        width: 100%;
        color: @bg-color;
        text-transform: uppercase;
        text-decoration: none;
        font-weight: 700;

        .main-nav__child-trigger + .main-nav__entry &::after {
            content: "👉"; //right
            padding-left: 1ch;
        }

        .main-nav__child-trigger:checked + .main-nav__entry & {
            display: none;
        }
    }

    &__child-trigger {
        display: none;
    }

    &__child-trigger-helper {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        cursor: pointer;

        &::after {
            content: "👈"; //left
            display: flex;
            align-items: center;
            justify-content: center;
            width: 30px;
            height: 30px;
            margin-left: -110%;
            color: @bg-color;
            transition: transform @transition;
        }

        .main-nav__child-trigger:checked ~ .main-nav__entry &::after {
            transform: translateX(100%);
        }
    }

    &__list--is-sub {
        top: 0;

        .main-nav__child-trigger:checked + .main-nav__entry + & {
            opacity: 1;
            transform: translateX(0);
            z-index: @z-nav + 1;
        }
    }
}

.content {
    &:extend(.container);
    padding: var(--header-height) 10px 10px;
    color: @text-color;
}

@media screen and (min-width: @break-m) {
    * {
        --header-height: 120px;
    }

    .header {
        position: relative;
        max-width: none;
    }

    .main-nav {
        position: sticky;
        top: -120px;

        &__burger-helper {
            display: none;
        }

        &__list {
            position: relative;
            display: flex;
            justify-content: center;
            align-items: center;
            width: 100%;
            max-width: none;
            height: auto;
            padding: 0;
            background-color: @primary-color;
            transform: translateX(0);
            overflow: visible;

            &--is-sub {
                position: absolute;
                background-color: darken(@primary-color, 5%);
                opacity: 0;
                pointer-events: none;
                z-index: -2;

                .main-nav__entry:hover + &,
                &:hover {
                    transform: translateY(40px);
                    opacity: 1;
                    pointer-events: all;
                }
            }
        }

        &__link {
            position: relative;
            justify-content: center;
            width: auto;
            padding: 10px 20px;

            .main-nav__child-trigger + .main-nav__entry &::after {
                content: "👇"; //down
            }
        }

        &__child-trigger-helper {
            display: none;
        }
    }
}

// no js