body {
    background-color: olivedrab;
}

.topnav {
    background-color: #333;
    overflow: hidden;
}

.topnav a {
    float: left;
    color: #f2f2f2;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 17px;
}

.topnav a:hover {
    background-color: #ddd;
    color: black;
}

.topnav a.active {
    background-color: #04aa6d;
    color: white;
}

.emergent_layer {
    width: 100%;
}

.canopy_layer {
    width: 100%;
}

.understory_layer {
    width: 100%;
}

.floor_layer {
    width: 100%;
}

.emergent {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.emergent .content {
    position: absolute;
    bottom: 0;
    background: rgb(0, 0, 0);
    background: rgba(0, 0, 0, 0.5);
    color: #f1f1f1;
    width: 95%;
    padding: 20px;
}

.canopy {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.canopy .content {
    position: absolute;
    bottom: 0;
    background: rgb(0, 0, 0);
    background: rgba(0, 0, 0, 0.5);
    color: #f1f1f1;
    width: 95%;
    padding: 20px;
}

.understory {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.understory .content {
    position: absolute;
    bottom: 0;
    background: rgb(0, 0, 0);
    background: rgba(0, 0, 0, 0.5);
    color: #f1f1f1;
    width: 95%;
    padding: 20px;
}

.floor {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.floor .content {
    position: absolute;
    bottom: 0;
    background: rgb(0, 0, 0);
    background: rgba(0, 0, 0, 0.5);
    color: #f1f1f1;
    width: 95%;
    padding: 20px;
}