* {
    box-sizing: border-box;
}

html,
body {
    height: 100%;
}

body {
    display: flex;
    flex-direction: column;
    width: 100%;
    margin: 0;
    box-sizing: border-box;
    background-color: #1b1b1e;
    font-family: Montserrat, sans-serif;
    color: #b1b1b3;
}

ul,
ol {
    list-style-type: none;
    margin: 0;
    padding: 0;
}

a {
    text-decoration: none;
    color: inherit;
}

header {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
}

.header__logo {
    display: block;
    width: 82px;
    margin: 1em auto;
}

main {
    margin: auto;
}

.visually-hidden { /* https://snook.ca/archives/html_and_css/hiding-content-for-accessibility */
    position: absolute !important;
    width: 1px;
    height: 1px; 
    margin: 0;
    overflow: hidden;
    clip: rect(1px 1px 1px 1px); /* IE6, IE7 */
    clip: rect(1px, 1px, 1px, 1px);
}

  #particles-js {
    position: absolute;
    width: 100%;
    height: 100%;
    background-image: url("");
    background-repeat: no-repeat;
    background-size: cover;
    background-position: 50% 50%;
    z-index: -1;
    overflow: hidden;
  }
  
.window {
    width: 700px;
    height: 500px;
    background-color: #000;
    box-shadow: 0 0 25px -7px #000;
}

.window-top {
    display: flex;
    align-items: center;
    height: 30px;
    background-color: #202020;
}

.window__controls {
    display: inline-flex;
}

.window__controls span {
    width: 15px;
    height: 15px;
    margin-left: 10px;
    border-radius: 50%;
}

.window__controls span:nth-child(1) {background-color: #b22222;}
.window__controls span:nth-child(2) {background-color: #d6bf3e;}
.window__controls span:nth-child(3) {background-color: #4db434;}

.window__title {
    flex: 1;
    text-align: center;
    color: #b1b1b3;
}

.window-main {
    padding: 0.5em;
    color: #4e4e4e;
}

.window-main ol {
    counter-reset: item;
    list-style-type: none;
    margin: 0;
    padding: 0;
    font-family: 'Source Code Pro', monospace;
}

.window-main ol li {
    margin-bottom: 3px;
}

.window-main ol li:before { 
    content: counter(item) "  "; 
    counter-increment: item;
    padding: 0 10px;
}

.tag {color: #4d86b9;}
.attr {color: #8dc6e3;}
.val {color: #c58b74;}
.text {color: #d4d4d4;}
.comment {color: #517343;}

footer {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 1em;
    border-top: 1px solid #4e4e4e;
    color: #fff;
    background-color: #1b1b1ece;
}

footer ul li {
    float: left;
    margin: 0 1em;
}

footer img {
    max-height: 15px;
}

.contact {
    font-size: 0.9em;
    font-weight: 700;
}

@media only screen and (max-width: 601px) {
	.header__logo {
        width: 64px;
        margin: 0.5em auto;
    }
	
    .window {
        width: 350px;
        height: 350px;
        font-size: 0.65em;
    }

    .window__controls span {
        width: 10px;
        height: 10px;
        margin-left: 5px;
    }

    .window-main ol li:before {
        padding: 0;
    }
}