div {
    margin: 2em 0 1em 0;
}

p {
    margin: 0;
    padding: 0;
}

img {
    max-width: 100%;
}

.indent1 {
    padding-left: 2em;
}

.indent2 {
    padding-left: 4em;
}

.indent3 {
    padding-left: 4em;
}

details {
    margin: 4px 4px;
    padding: 0 4px 4px 4px;
}

details label {
    padding: 6px;
    pointer-events: none;
    cursor: pointer;
}

details:not([open]) {
    border: gray 1px solid;
}

details:not([open]):hover {
    box-shadow: 1px 1px 1px darkgrey;
    cursor: pointer;
}

details[open] {
    border: gray 1px solid;
}

details[open] summary {
    padding: 6px;
}

details[open] summary:hover {
    cursor: pointer;
}

summary {
    display: flex;
    align-items: center;
    padding-left: 4px;
}

pre {
    background-color: rgba(128, 128, 128, 0.3);
    padding: 4px;
    border: dashed 1px gray;
}

blockquote {
    background-color: beige;
    border: solid 1px darkgoldenrod;
    padding: 4px;
    font-style: italic;
}

blockquote > .cite {
    display: flex;
    justify-content: flex-end;
}

blockquote > .cite::before {
    content: "引用元：";
}