:root {
  color-scheme: light;
  --paper: #f7f5ed;
  --ink: #1e2823;
  --muted: #505c53;
  --pine: #14523f;
  --rust: #853e2a;
  --line: #d3d9cc;
  --body: system-ui, "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --title: "Songti SC", "Noto Serif CJK SC", SimSun, serif;
  --mono: ui-monospace, Consolas, monospace;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-padding-top: 1.5rem; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 1rem/1.75 var(--body); }
::selection { color: var(--ink); background: #dddec2; }
a { color: inherit; text-underline-offset: .24em; }
a:where(:hover, :focus-visible) { color: var(--pine); }
a:focus-visible { outline: 2px solid var(--rust); outline-offset: 5px; }
p, h1, h2, h3, h4, figure { margin: 0; }
h1, h2, h3, h4 { overflow-wrap: anywhere; }
.shell { width: min(73rem, calc(100% - 5rem)); margin-inline: auto; }
.skip { position: fixed; left: 1rem; top: 1rem; z-index: 2; transform: translateY(-150%); background: var(--paper); padding: .6rem 1rem; }
.skip:focus { transform: none; }

.masthead { min-height: 5rem; display: flex; align-items: center; justify-content: space-between; gap: 1rem; border-bottom: 1px solid var(--line); }
.wordmark { display: inline-flex; align-items: center; gap: .7rem; font-weight: 760; text-decoration: none; white-space: nowrap; }
.stamp { display: grid; place-items: center; inline-size: 2.1rem; block-size: 2.1rem; border-radius: .15rem; background: var(--pine); color: var(--paper); font: 700 1.2rem/1 var(--title); }
.wordmark-sub { margin-left: .65rem; font-size: .77rem; font-weight: 500; color: var(--muted); }
.masthead nav, .footer nav { display: flex; flex-wrap: wrap; align-items: center; justify-content: end; gap: .25rem clamp(.8rem, 3vw, 2rem); }
.masthead nav a, .footer nav a { display: inline-block; text-decoration: none; font-size: .88rem; padding-block: .4rem; }
.masthead nav a:hover, .footer nav a:hover { text-decoration: underline; }

.hero { padding-block: clamp(3.75rem, 8vw, 7rem); display: grid; grid-template-columns: 1.18fr 1fr; gap: clamp(2rem, 6vw, 6rem); align-items: center; }
.eyebrow { color: var(--pine); font: 650 .78rem/1.5 var(--mono); letter-spacing: .1em; }
.eyebrow > span { display: inline-block; width: .46em; height: .46em; background: var(--rust); vertical-align: .18em; margin-right: .5em; }
h1 { margin-top: 1.2rem; font: 800 clamp(2.8rem, 5.85vw, 5.3rem)/1.18 var(--title); letter-spacing: -.045em; }
.intro { margin-top: 1.55rem; max-width: 29em; color: var(--muted); font-size: 1.04rem; }
.hero-actions { margin-top: 1.65rem; display: flex; flex-wrap: wrap; align-items: center; gap: .7rem 1.25rem; font-size: .87rem; font-weight: 650; }
.button { display: inline-flex; align-items: center; gap: .75rem; text-decoration: none; background: var(--pine); color: white; border-radius: .18rem; padding: .58rem 1rem; }
.button:where(:hover, :focus-visible) { background: #214334; color: white; }
.inline-link { color: var(--pine); padding-block: .58rem; }

.notebook { display: flex; flex-direction: column; min-height: 19rem; border: 1px solid #c5d1c3; background-color: #edf0e5; background-image: linear-gradient(#55836c17 1px, transparent 1px), linear-gradient(90deg, #55836c17 1px, transparent 1px); background-size: 1.35rem 1.35rem; }
.notebook-meta, .notebook figcaption { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: .25rem .8rem; padding: .8rem 1rem; color: var(--pine); background: #edf0e5; font: 650 .77rem/1.55 var(--mono); }
.notebook-meta { border-bottom: 1px solid #c5d1c3; }
.notebook figcaption { border-top: 1px solid #c5d1c3; }
.notebook-body { flex: 1; display: grid; align-content: center; justify-items: center; gap: 1rem; padding: 2.25rem .75rem; }
.formula { display: flex; align-items: center; justify-content: center; gap: .45em; font: italic clamp(1.04rem, 2.35vw, 1.97rem)/1.1 Georgia, serif; white-space: nowrap; }
.fraction { display: inline-grid; text-align: center; }
.fraction span { padding: .25em .24em; }
.fraction span:first-child { border-bottom: 1px solid currentColor; }
.margin-note { color: var(--rust); font-size: .86rem; text-align: center; }
.margin-note span { margin-right: .3em; font-weight: 800; }

.chapter { border-top: 1px solid var(--ink); padding-block: clamp(2.2rem, 5vw, 4rem) clamp(3rem, 6vw, 5.5rem); }
.section-head { display: flex; justify-content: space-between; align-items: end; flex-wrap: wrap; gap: .55rem 2rem; margin-bottom: clamp(1.4rem, 3vw, 2.1rem); }
h2 { font: 800 clamp(1.9rem, 4vw, 3.2rem)/1.22 var(--title); letter-spacing: -.035em; margin-top: .38rem; }
.section-head > p { color: var(--muted); font-size: .88rem; }
.books { border-top: 1px solid var(--line); }
.book { display: grid; grid-template-columns: 3.85rem minmax(0, 1fr) minmax(9.4rem, auto); gap: .75rem clamp(.8rem, 3.4vw, 2.5rem); padding: 1.5rem .2rem; border-bottom: 1px solid var(--line); }
.book-index { font: italic 2.3rem/1.1 Georgia, serif; color: var(--pine); padding-top: .32rem; }
.book-status { font-size: .75rem; font-weight: 660; color: var(--muted); letter-spacing: .05em; }
.published { color: var(--rust); }
.book h3 { margin: .38rem 0 .44rem; font: 760 clamp(1.21rem, 2.3vw, 1.75rem)/1.35 var(--title); }
.book h3 span { display: inline-block; margin-left: .65rem; color: var(--pine); font-size: .64em; }
.book-info > p:last-child { max-width: 38em; color: var(--muted); font-size: .92rem; }
.book-links { display: grid; align-content: center; gap: .35rem; justify-items: start; }
.book-links a, .work-links a { color: var(--pine); font-size: .82rem; font-weight: 650; }
.book-links a:hover, .work-links a:hover { color: var(--rust); }

.reading-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: clamp(1.7rem, 5vw, 4rem); }
.route-head { display: flex; align-items: center; gap: .85rem; border-bottom: 1px solid var(--line); padding: .75rem .9rem; background: #e9ede2; }
.route-ai .route-head { background: #eee9df; }
.route-head h3 { font: 730 1.42rem/1.25 var(--title); }
.route-symbol { width: 1.35em; color: var(--pine); text-align: center; font: italic 1.65rem/1.1 Georgia, serif; }
.route-ai .route-symbol { color: var(--rust); }
.route ol { list-style: none; margin: 0; padding: 0; counter-reset: step; }
.route li { position: relative; border-bottom: 1px solid var(--line); padding: 1.15rem 0 1.1rem 1.75rem; counter-increment: step; }
.route li::before { content: counter(step, decimal-leading-zero); position: absolute; top: 1.4rem; left: 0; color: var(--muted); font: .75rem/1 var(--mono); }
.route h4 { font-size: .98rem; line-height: 1.48; }
.route li p { margin-top: .28rem; font-size: .88rem; color: var(--muted); }
.work-links { margin-top: .42rem; display: flex; flex-wrap: wrap; gap: .2rem 1rem; }
.footer { display: flex; align-items: end; justify-content: space-between; flex-wrap: wrap; gap: 1rem 2rem; border-top: 1px solid var(--ink); padding-block: 1.8rem 2.75rem; }
.footer h2 { font-size: 1.48rem; }
.side-topic { padding-block: 1.7rem; }
.side-topic .section-head { align-items: center; margin-bottom: 0; }
.side-topic h2 { font-size: clamp(1.48rem, 3vw, 2rem); }
.side-topic .inline-link { font-size: .88rem; }
.topic-intro { margin-top: .85rem; color: var(--muted); }
.topic-entry h2 { margin-top: 0; }
.archive-list li { margin-block: .45em; }
.archive-list small, .archive-list time { color: var(--muted); font-size: .78rem; }
.archive-list time { display: inline-block; margin-inline-start: .35em; }
.archive-list ol { padding-inline-start: 1.5em; }
.prose table { display: block; max-width: 100%; overflow-x: auto; border-collapse: collapse; }
.prose :is(th, td) { border: 1px solid var(--line); padding: .35em .55em; }

.article-page { max-width: 49rem; margin-inline: auto; }
.article-head { border-bottom: 1px solid var(--line); padding-block: clamp(2rem, 6vw, 4.5rem) 1.6rem; }
.article-head h1 { font-size: clamp(1.95rem, 6vw, 3.65rem); line-height: 1.28; }
.article-meta { margin-top: .8rem; color: var(--muted); font-size: .85rem; }
.prose { padding-block: 1.35rem 2.3rem; line-height: 1.9; overflow-wrap: anywhere; }
.prose p, .prose ul { margin: 0 0 1.1rem; }
.prose ul { padding-left: 1.35em; }
.prose li + li { margin-top: .6rem; }
.prose h2 { margin: 2rem 0 .9rem; font-size: clamp(1.25rem, 4vw, 1.6rem); line-height: 1.4; }
.prose hr { margin-block: 1.75rem; border: 0; border-top: 1px solid var(--line); }
.prose figure { margin: 1.15rem 0 1.65rem; }
.prose img { display: block; max-width: 100%; height: auto; background: #fff; border: 1px solid var(--line); }
.prose figcaption { margin-top: .45rem; color: var(--muted); font-size: .84rem; }
.prose math { font-size: 1em; }
.prose .equation-block { overflow-x: auto; text-align: center; padding: .5rem .1rem; }
.prose pre { margin: 1rem 0; overflow-x: auto; padding: 1rem; border: 1px solid var(--line); background: #eeeee4; }
.prose code { font: .83rem/1.65 var(--mono); }
.article-footer { display: flex; flex-wrap: wrap; justify-content: space-between; gap: .6rem 1rem; border-top: 1px solid var(--line); padding-block: 1.25rem 2.3rem; color: var(--pine); font-size: .86rem; }

@media (max-width: 760px) {
  .shell { width: calc(100% - 2.5rem); }
  .hero { grid-template-columns: minmax(0, 1fr); gap: 1.8rem; }
  h1 { font-size: clamp(2.35rem, 9vw, 4.5rem); }
  .formula { font-size: clamp(1.12rem, 5vw, 1.92rem); }
  .book { grid-template-columns: 2.4rem minmax(0, 1fr); }
  .book-links { grid-column: 2; display: flex; flex-wrap: wrap; gap: .3rem 1rem; }
  .book-index { font-size: 1.7rem; }
  .book h3 span { display: block; margin-left: 0; margin-top: .2em; }
  .reading-grid { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 380px) {
  .shell { width: calc(100% - 2rem); }
  .wordmark-sub { display: none; }
}