*, *:before, *:after {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    position: relative;
}

.root {
    height: 100vh;
    width: 100vw;
}

.Resizer {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    background: #000;
    opacity: .2;
    z-index: 1;
    -moz-background-clip: padding;
    -webkit-background-clip: padding;
    background-clip: padding-box;
}

.Resizer:hover {
    -webkit-transition: all 2s ease;
    transition: all 2s ease;
}

.Resizer.horizontal {
    height: 11px;
    margin: -5px 0;
    border-top: 5px solid rgba(255, 255, 255, 0);
    border-bottom: 5px solid rgba(255, 255, 255, 0);
    cursor: row-resize;
    width: 100%;
}

.Resizer.horizontal:hover {
    border-top: 5px solid rgba(0, 0, 0, 0.5);
    border-bottom: 5px solid rgba(0, 0, 0, 0.5);
}

.Resizer.vertical {
    width: 11px;
    margin: 0 -5px;
    border-left: 5px solid rgba(255, 255, 255, 0);
    border-right: 5px solid rgba(255, 255, 255, 0);
    cursor: col-resize;
}

.Resizer.vertical:hover {
    border-left: 5px solid rgba(0, 0, 0, 0.5);
    border-right: 5px solid rgba(0, 0, 0, 0.5);
}

.vertical section {
    width: 100vh;
    height: 100vh;
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: normal;
    -webkit-flex-direction: column;
        -ms-flex-direction: column;
            flex-direction: column;
}

.vertical header {
    padding: 1rem;
    background: #eee;
}

.vertical footer {
    padding: 1rem;
    background: #eee;
}

#vertically-nested-in-container-example {
    -webkit-box-flex: 1;
    -webkit-flex: 1;
        -ms-flex: 1;
            flex: 1;
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
}

.horizontal section {
    width: 100vh;
    height: 100vh;
    display: flex;
    flex-direction: column;
}

.horizontal header {
    padding: 1rem;
    background: #eee;
}

.horizontal footer {
    padding: 1rem;
    background: #eee;
}

#horizontally-nested-in-container-example {
    flex: 1;
    display: flex;
}

.parent {
    width: 100%;
    height: 100%;
    -webkit-box-flex: 1;
    -webkit-flex: 1;
        -ms-flex: 1;
            flex: 1;
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: normal;
    -webkit-flex-direction: column;
        -ms-flex-direction: column;
            flex-direction: column;
}
.header {
    background: #aaa;
    height: 3rem;
    line-height: 3rem;
}
.wrapper {
    background: #ffa;
    margin: 5rem;
    -webkit-box-flex: 1;
    -webkit-flex: 1;
        -ms-flex: 1;
            flex: 1;
}