:root {
    --paper: #f5f1e8;
    --ink: #2a2926;
    --muted: #666155;
    --line: #cfc7b8;
    --accent: #2b5f6a;
}

body {
    font-family: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", "Times New Roman", serif;
    background: var(--paper);
    color: var(--ink);
}

html {
    scroll-behavior: smooth;
}

a {
    text-decoration: none;
}

.prose {
    color: var(--ink);
    font-size: 1.05rem;
}

.prose p {
    margin-bottom: 1rem;
    line-height: 2;
}

.prose strong {
    color: var(--ink);
}

.subject-fold summary::-webkit-details-marker {
    display: none;
}

.subject-fold summary::after {
    content: "+";
    float: right;
    color: var(--muted);
}

.subject-fold[open] summary::after {
    content: "-";
}

.back-to-top {
    position: fixed;
    right: 1.25rem;
    bottom: 1.25rem;
    width: 2.25rem;
    height: 2.25rem;
    border: 1px solid var(--line);
    background: rgba(245, 241, 232, 0.95);
    color: var(--muted);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    line-height: 1;
}

.back-to-top:hover {
    color: var(--accent);
    border-color: var(--accent);
}