cssOMS/nav.scss

body > nav {
    width: 250px;
    overflow-y: auto;
    font-size: 0.8em;
    background: linear-gradient(135deg, var(--nav-category-background-highlight), var(--nav-category-background));
    color: rgba(255, 255, 255, 0.8);
}

#nav-side {
    flex: 0;
    display: flex;
    flex-flow: column;
    box-sizing: border-box;

    span {
         width: 20px;
         display: inline-block;
    }

    input {
        display: none;

        &:checked + ul {
            .max {
                display: inherit;
            }

            .min {
                display: none;
            }

            > li:nth-child(n+2) {
                display: inherit;
            }
        }
    }

    input + ul {
        .min, .max {
            margin-left: 1rem;
            float: right;
        }

        .max {
            display: none;
        }

        .min {
            display: inherit;
        }

        > li:nth-child(n+2) {
            display: none;
        }
    }

    label {
        display: block;
        padding: .5rem 1rem .5rem 1rem;
        cursor: pointer;
    }

    > li {
        display: block;

        a {
            display: block;
            padding: .5rem 1rem .5rem 1rem;

            &:hover {
                background: var(--nav-sub-background-hover);
            }
        }

        li {
            &:not(:first-child) {
                background: linear-gradient(to right, var(--nav-sub-background-highlight), var(--nav-sub-background));
            }

            &:hover, &.active {
                background: var(--nav-category-background-hover);
            }
        }
    }

    .max, .min {
        float: right;
    }

    i {
        margin-right: 5px;
    }
}

.nav-trigger {
    position: absolute;
    clip: rect(0, 0, 0, 0);

    &:checked + nav {
        width: 0%;
    }
}

.nav-top {
    user-select: none;
    margin-top: 1rem;
    display: block;
    background: #fff;
    border: 1px solid var(--box-border);

    > li {
        > a {
            display: inline-block;
            padding: 10px 10px;
        }
    }

    li {
        background: #fff;
        display: inline-block;
        position: relative;
        cursor: pointer;

        &:hover, &.active {
            background: var(--nav-content-hover);
            color: var(--text-on-background-color-2);

            > ul {
                display: block;
                opacity: 1;
                visibility: visible;
            }
        }

        > ul {
            padding: 0;
            z-index: 5;
            position: absolute;
            top: 36px;
            left: 0;
            width: 150px;
            display: none;
            opacity: 0;
            visibility: hidden;

            li {
                display: block;
                color: #000;
                padding: 7px;

                &:hover {
                    color: #252525;
                    background: var(--nav-content-hover);
                }
            }
        }
    }
}

@media only screen and (max-width: 800px) {
    #nav-trigger:not(:checked) + nav {
        width: 0%;
    }

    #nav-trigger:checked + nav {
        width: auto;
    }
}

@media only screen and (max-width: 500px) {
    #nav-trigger:checked + nav {
        width: 100%;
    }

    #nav-trigger:checked ~ main {
        display: none;
    }
}