client/themes/material/css/block.css

.flex {
    display: flex;
    flex-flow: row wrap;
}

.flex .block:not(.subheader) {
    flex: 0 1 50%;
    overflow: hidden;
    padding: 0;
}

.flex.card .block:not(.subheader) {
    margin: 0.75rem;
    flex: 0 1 calc(50% - 1.5rem);
    min-height: 5rem;
    padding-top: 1.5rem;
    padding-bottom: 1.5rem;
}

.flex.stacked .block:not(.subheader) {
    margin-bottom: 0;
}

.flex.third {
    flex-flow: row wrap;
}

.flex.third .block:not(.large) {
    flex: 0 1 calc(33.33% - 1.5rem);
    max-width: calc(33.33% - 1.5rem);
}


.flex .block.large,
.flex.card .block.large {
    flex: 0 1 100%;
}

.column {
    column-count: 3;
    margin: 1rem 0;
}

.column.half {
    column-count: 2;
}

.column > * {
    display: inline-block;
    width: 100%;
}

@media screen and (max-width: 612px) {
    .flex.card .block:not(.subheader),
    .flex .block:not(.subheader),
    .flex.third .block:not(.subheader) {
        margin-bottom: 0;
        flex: 0 1 100%;
        max-width: 100%;
    }

    .column,
    .column.half {
        column-count: 1;
    }
}

@media screen and (min-width: 613px) and (max-width: 1024px) {
    .flex.card .block:not(.subheader),
    .flex .block:not(.subheader),
    .flex.third .block:not(.subheader) {
        flex: 0 1 calc(50% - 1.5rem);
        max-width: 100%;
    }

    .column {
        column-count: 2;
    }
}