画像ブロック｜画像リンク（四角ライン）

bf-img-link--square-border

.bf-img-link--square-border {
    outline: 2px solid #fff;
    outline-offset: -1.5rem;
    position: relative;
    display: flex;
    transition: outline-offset 0.3s ease-out;
}
.bf-img-link--square-border:hover {
    outline-offset: 0;
}
.bf-img-link--square-border figcaption {
    font-size: 1.5rem;
    font-weight: 600;
    color: #fff;
    text-shadow: 0 2px 4px rgb(51 51 51 / 0.3);
    position: absolute;
    margin: 0;
    align-self: center;
    width: 100%;
    text-align: center;
    padding: 1rem;
    box-sizing: border-box;
}
.bf-img-link--square-border a:after {
    content: "";
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: 1;
}