.item {
    float: left;
    position: relative;
    line-height: 1em;
}


.grid-sizer {
    width: 25%;
}

.item {
    width: 25%;
    padding: 10px;
}


@media screen and (max-width: 1224px) {
    /* 10 columns for larger screens */
    .grid-sizer {
        width: 33.33%;
    }

    .item {
        width: 33.33%;
    }
}

@media screen and (max-width: 720px) {
    /* 10 columns for larger screens */
    .grid-sizer {
        width: 50%;
    }

    .item {
        width: 50%;
    }
}

@media screen and (max-width: 480px) {
    /* 10 columns for larger screens */
    .grid-sizer {
        width: 100%;
    }

    .item {
        width: 100%;
    }
}

.image {
    max-width: 100%;
    margin: 0;
    display: block;
    filter: none;
    -moz-filter: none;
    -webkit-filter: none;
    filter: grayscale(0);
    -moz-filter: grayscale(0);
    -webkit-filter: grayscale(0);
}

    .image:hover {
        filter: gray;
        -moz-filter: gray;
        -webkit-filter: gray;
        filter: grayscale(1);
        -webkit-filter: grayscale(1);
        -moz-filter: grayscale(1);
        transition: all 0.3s ease-in-out;
        -webkit-transition: all 0.3s ease-in-out;
        -moz-transition: all 0.3s ease-in-out;
    }

    .image:after {
        clear: both;
    }

.overlay {
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.8);
    position: absolute;
    top: 0;
    left: 0;
    text-decoration: none;
    color: #fff;
    display: none;
    border: 10px solid #fff;
}

    .overlay .title {
        text-align: center;
        font-size: 20px;
        font-family: Roboto;
        padding-top: 10%;
        color: #fff;
    }

.item:hover .overlay {
    display: block;
}