* {
    box-sizing: border-box;
}

#container,
.container {
    background: #EEE;
    width: 50%;
    margin-bottom: 20px;
}

.item {
    width: 60px;
    height: 60px;
    float: left;
    border: 1px solid;
    background: #09F;
}

.item.w2 {
    width: 120px;
}

.item.w3 {
    width: 180px;
}

.item.h2 {
    height: 100px;
}

.item.h3 {
    height: 160px;
}

.item.h4 {
    height: 220px;
}

.item.h5 {
    height: 280px;
}

.stamp {
    background: red;
    opacity: 0.75;
    position: absolute;
    border: 1px solid;
}

/* element */

.element {
    width: 80px;
    height: 90px;
    margin: 5px;
    background: #DDD;
    float: left;
    position: relative;
    padding: 5px;
}

.element > * {
    margin: 0;
}

.element .number {
    right: 5px;
    top: 5px;
    position: absolute;
}

.element .symbol {
    font-size: 30px;
    left: 5px;
    top: 5px;
    color: white;
}

.element .name {
    font-size: 14px;
}

.element .weight {
    font-size: 14px;
}

.element.alkali {
    background: #F00;
    background: hsl(0, 100%, 50%);
}

.element.alkaline-earth {
    background: #F80;
    background: hsl(36, 100%, 50%);
}

.element.lanthanoid {
    background: #FF0;
    background: hsl(72, 100%, 50%);
}

.element.actinoid {
    background: #0F0;
    background: hsl(108, 100%, 50%);
}

.element.transition {
    background: #0F8;
    background: hsl(144, 100%, 50%);
}

.element.post-transition {
    background: #0FF;
    background: hsl(180, 100%, 50%);
}

.element.metalloid {
    background: #08F;
    background: hsl(216, 100%, 50%);
}

.element.other.nonmetal {
    background: #00F;
    background: hsl(252, 100%, 50%);
}

.element.halogen {
    background: #F0F;
    background: hsl(288, 100%, 50%);
}

.element.noble-gas {
    background: #F08;
    background: hsl(324, 100%, 50%);
}

/* stamps */

.stamp {
    position: absolute;
    background: hsla(0, 100%, 50%, 0.8);
    border: 1px solid;
}

.stamp1 {
    left: 10%;
    top: 20px;
    width: 20%;
    height: 200px;
}

.stamp2 {
    right: 200px;
    top: 100px;
    width: 100px;
    height: 100px;
}