#app {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;

    margin: 0;
    padding: 0;

    display: flex;
    flex-direction: column;                
}

header {
    border-bottom: 2px solid black;
}

header h1 {
    display: inline-block;
    padding: 5px;
    margin: 0;
    font-size: 15px;
}

header h1 .title {
    font-size: 20px;
}

header ul {
    display: inline-block;
    margin: 0;
    padding: 0;
    border-left: 2px solid black;
}

header ul li {
    display: inline-block;
    margin: 0;
    padding: 5px;
    border-right: 2px solid black;
}

header ul li.selected {
    background-color: yellow;
}

header ul li:hover {
    background-color: orange;
}

article {
    flex-grow: 1;
    flex-shrink: 1;
    min-height: 0;
    display: flex;                
}

#source {
    font-family: monospace;
    font-size: 12px;
    max-width: 50%;

    border-right: 2px solid black;
    display: flex;
    flex-direction: column;
}

#source h1 {
    background-color: #aaa;
    font-size: 14px;
    padding: 5px;
    margin: 0;
}

#source pre {
    padding: 5px;
    color: #ccc;
    overflow: auto;
}

#source pre b {
    color: #000;
    font-size: 1.1em;
}

#demo {
    flex-grow: 1;
    position: relative;
}

#demo iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}