.alt-portfolio {
    background-color: lightgrey;
    margin-bottom: 50px;
}

.alt-portfolio .thumb-container {
    max-width: 1000px;
    margin: auto;
    padding-top: 50px;
    padding-bottom: 50px;
}

.alt-portfolio .thumb-container::after {
    content: "";
    clear: both;
    display: table;
}

.alt-portfolio .thumb-container .thumb-unit {
    width: 33.33%;
    display: block;
    float: left;
    position: relative;
    padding-top: 17%;
    
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    overflow: hidden;
    perspective: 100px;
}

.alt-portfolio .thumb-container .thumb-unit .thumb-overlay {
    position: absolute;
    top: -50%;
    left: 0;
    right: 0;
    background: burlywood;
    height: 100%;

    opacity: 0.1;
    transition: 350ms;

    text-align: center;

    transform: rotateX(90deg);
    transform-origin: center bottom;
}

.alt-portfolio .thumb-container .thumb-unit:hover .thumb-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;

    opacity: 0.9;

    transform: rotateX(0deg);
}

.alt-portfolio .thumb-container .thumb-unit .thumb-overlay strong {
    display: block;
    padding: 20px;
    color: white;
    font-weight: 700;
    text-transform: uppercase;
    font-size: 20pt;
    line-height: 1.2;
}

.alt-portfolio .thumb-container .thumb-unit .thumb-overlay i {
    font-size: 20pt;
}

@media screen and (max-width: 830px) {
    .thumb-container .thumb-unit {
        width: 50%;
        padding-top: 23%;
    }

}

@media screen and (max-width: 550px) {
    .thumb-container .thumb-unit {
        width: 50%;
        padding-top: 30%;
    }
    .thumb-container .thumb-unit .thumb-overlay strong {
        padding: 5px;
        line-height: 1.1;
    }
}