Custom CSS for Jupyter Notebook web application

custom.css

#notebook-container{
    box-shadow: none !important;
}

.container {
    width: 80% !important;
}

.notebook_app {
    background: #fff !important;
}

body > #header {
    background:  #f57b00;
}

.navbar-default {
    background: none;
    border: none;
}

.navbar-default .navbar-nav > li > a, #kernel_indicator {
    color: rgba(255, 255, 255, 0.25);
    border-bottom: 2px solid #f57b00;
    transition: all 0.25s;
}

.navbar-default .navbar-nav > li > a:hover, #kernel_indicator:hover {
    border-bottom: 2px solid #fff;
    color: rgba(255, 255, 255, 1);
}

div.input_area {
    border: none;
    border-radius: 0;
    background: #f7f7f7;
    line-height: 1.5em;
    margin: 0.5em 0;
    padding: 0;
}

div.cell {
    transition: all 0.25s;
    border: none;
    position: relative;
    top: 0;
}

div.cell.selected, div.cell.selected.jupyter-soft-selected {
    border: none;
    background: transparent;
    box-shadow: 0 6px 18px #aaa;
    z-index: 10;
    top: -10px;
}


div#pager {
    opacity: 0.85;
    z-index: 9999;
}

.navbar-default .navbar-nav > .open > a, .navbar-default .navbar-nav > .open > a:hover, .navbar-default .navbar-nav > .open > a:focus {
    color: #fff;
    background-color: transparent;
    border-bottom: 2px solid #fff;
}

.dropdown-menu {
    z-index: 999999 !important;
    background-color: #f57b00;
    opacity: 0.95;
}

.dropdown-menu > li > a {
    color: #fff;
}

.dropdown-menu > .disabled > a, .dropdown-menu > .disabled > a:hover, .dropdown-menu > .disabled > a:focus {
    color: rgba(255, 255, 255, 0.25);
}

.navbar-nav > li > .dropdown-menu {
    border: none;
    box-shadow: none;
}

div.output_wrapper {
    background: #eee;
}

div.cell.unselected div.output_area{
    box-shadow: inset 0 0 25px #aaa;
    padding: 1em 0;
    overflow-x: auto;
    transition: all 0.25s;
}

div.cell.selected .output_area {
    box-shadow: inset 0 0 5px #aaa;
    padding: 0.5em 0;
    overflow-x: auto;
}

div.cell.selected .div.output_scroll {
    box-shadow: none;
}

div.output_wrapper {
    margin: 0 0 1em;
    transition: all 0.25s;
}

div.cell.selected .output_wrapper {
    margin: 0;
}

.dataframe {
    background: #fff;
    box-shadow: 0px 1px 2px #bbb;
}

.dataframe thead th, .dataframe tbody td {
    text-align: right;
    padding: 1em;
}

.output, div.output_scroll {
    box-shadow: none;
}

.rendered_html pre code {
    background: #f4f4f4;
    border: 1px solid #ddd;
    border-left: 3px solid #2a7bbd;
    color: #444;
    page-break-inside: avoid;
    font-family: monospace;
    font-size: 15px;
    line-height: 1.6;
    margin-bottom: 1.6em;
    max-width: 100%;
    overflow: auto;
    padding: 1em 1.5em;
    display: block;
    word-wrap: break-word;
}

h1, .h1 {
    font-size: 33px;
    font-family: "Trebuchet MS";
    font-size: 2.5em !important;
    color: #2a7bbd;
}

Theme preview:

Hi, do you now how to create jupyterLab's extensions ???