@charset "UTF-8";
:root {
  color-scheme: light;
  --ink: #202b35;
  --muted: #566574;
  --paper: #fbfaf6;
  --panel: #ffffff;
  --line: #d9dedb;
  --green: #166b56;
  --green-soft: #e7f2ec;
  --coral: #b64d36;
  --coral-soft: #fff0e9;
  --code: #172b32;
  --code-ink: #edf4ef;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font: 16px/1.75 "Microsoft YaHei", "PingFang SC", sans-serif;
}
header {
  padding: 2.5rem max(1rem, calc((100% - 900px) / 2));
  color: #fff;
  background: linear-gradient(115deg, #164d48, #22705c 68%, #43836d);
  border-bottom: 5px solid #d59a55;
}
header .eyebrow { margin: 0 0 .45rem; color: #d7eadf; font-size: .85rem; }
h1 { margin: 0; font-size: clamp(1.65rem, 4vw, 2.5rem); line-height: 1.25; }
header p { max-width: 700px; margin: .8rem 0 0; color: #e8f2eb; }
main { width: min(900px, calc(100% - 2rem)); margin: 2rem auto 3rem; }
main.lesson-page { width: 95%; max-width: none; margin-bottom: .5rem; }
.lesson-columns { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; align-items: start; }
.lesson-column { position: sticky; top: 0; height: 100vh; height: 100dvh; min-width: 0; overflow-y: auto; overscroll-behavior: contain; padding-right: .5rem; scrollbar-gutter: stable; scrollbar-color: #9aafa5 #edf0eb; scrollbar-width: thin; }
.lesson-column > section:first-child { margin-top: 1.25rem; }
section { margin: 1.25rem 0; padding: 1.25rem clamp(1rem, 3vw, 1.6rem); background: var(--panel); border: 1px solid var(--line); border-radius: 6px; }
h2 { margin: 0 0 .75rem; color: var(--green); font-size: 1.25rem; }
h3 { margin: 1rem 0 .35rem; font-size: 1.03rem; }
p { margin: .45rem 0; }
ul, ol { padding-left: 1.4rem; }
li { margin: .35rem 0; }
code { padding: .08rem .32rem; color: #8e3f2d; background: #f8eee8; border-radius: 3px; font-family: Consolas, "Cascadia Code", monospace; }
pre { overflow-x: auto; margin: .7rem 0; padding: 1rem; color: var(--code-ink); background: var(--code); border-left: 4px solid #d59a55; border-radius: 4px; line-height: 1.55; }
pre code { padding: 0; color: inherit; background: transparent; }
.python-code .kw { color: #f4a261; }
.python-code .module { color: #82c9a8; }
.python-code .func { color: #8ecae6; }
.python-code .str { color: #f6bd60; }
.python-code .num { color: #cdb4db; }
.python-code .comment { color: #a5b4a8; font-style: italic; }
.python-code .name { color: #f3f4ed; }
table { width: 100%; border-collapse: collapse; margin: .7rem 0; }
th, td { padding: .55rem .65rem; border: 1px solid var(--line); text-align: left; vertical-align: top; }
th { background: var(--green-soft); }
.note { padding: .7rem .9rem; background: var(--coral-soft); border-left: 4px solid var(--coral); }
.tip { padding: .7rem .9rem; background: var(--green-soft); border-left: 4px solid var(--green); }
.steps { counter-reset: step; list-style: none; padding: 0; }
.steps li { counter-increment: step; padding: .35rem 0 .35rem 2.4rem; position: relative; }
.steps li::before { content: counter(step); position: absolute; left: 0; width: 1.7rem; height: 1.7rem; color: white; background: var(--green); border-radius: 50%; text-align: center; line-height: 1.7rem; }
nav { display: flex; justify-content: space-between; gap: 1rem; margin: 1.5rem 0; }
nav a, .backlink { color: var(--green); font-weight: 700; }
footer { padding: 1.3rem 1rem 2rem; color: var(--muted); text-align: center; }
.lesson-footer { width: 95%; margin: .2rem auto .5rem; padding: .25rem 0; display: flex; justify-content: space-between; align-items: center; gap: 1rem; color: var(--muted); text-align: left; }
.lesson-footer a { color: var(--green); font-weight: 700; }
.lesson-nav { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: .8rem; }
@media (max-width: 600px) {
  header { padding: 1.7rem 1rem; }
  main { width: min(100% - 1rem, 900px); margin-top: 1rem; }
  section { padding: 1rem; }
  table { font-size: .92rem; }
  th, td { padding: .4rem; }
}
@media (max-width: 850px) {
  .lesson-columns { grid-template-columns: minmax(0, 1fr); gap: 0; }
  main.lesson-page { width: calc(100% - 1rem); }
  .lesson-column { position: static; height: auto; max-height: none; overflow: visible; padding-right: 0; scrollbar-gutter: auto; }
}
@media (max-width: 600px) {
  .lesson-footer { width: calc(100% - 1rem); flex-wrap: wrap; gap: .25rem 1rem; }
}
.index-header { padding: 2.5rem 2.5%; }
.index-page { width: 95%; max-width: none; margin: 1.5rem auto 2rem; }
.index-tools { display: grid; grid-template-columns: minmax(180px, .6fr) minmax(260px, 1.8fr) minmax(120px, .5fr); align-items: center; gap: 1rem; margin: 0 0 2rem; padding: 1rem 1.25rem; background: var(--panel); border: 1px solid var(--line); border-radius: 6px; }
.index-tools label { font-weight: 700; }
#lesson-search { width: 100%; padding: .7rem .8rem; color: var(--ink); background: var(--paper); border: 1px solid #aab5af; border-radius: 4px; font: inherit; }
#lesson-search:focus { outline: 3px solid #b9d9cb; border-color: var(--green); }
#search-status { margin: 0; color: var(--muted); text-align: right; }
.index-group { margin: 2rem 0; padding: 1.15rem 0 0; background: transparent; border: 0; border-top: 2px solid var(--line); border-radius: 0; }
.group-heading { display: flex; align-items: center; gap: 1.1rem; margin: 0 0 .75rem; }
.group-heading h2 { margin: 0; color: var(--ink); }
.group-heading p { margin: .15rem 0 0; color: var(--muted); }
.group-range { min-width: 4.4rem; color: var(--coral); font: 700 1.1rem/1.2 Consolas, monospace; }
.lesson-list { border-top: 1px solid var(--line); }
.lesson-row { display: grid; grid-template-columns: 3rem minmax(0, 1fr) minmax(230px, 290px); align-items: center; gap: 1rem; padding: .9rem .5rem; border-bottom: 1px solid var(--line); }
.lesson-number { color: var(--muted); font: 700 1rem Consolas, monospace; }
.lesson-info h3 { margin: 0; color: var(--green); font-size: 1.02rem; }
.lesson-info p { margin: .12rem 0 0; color: var(--muted); font-size: .93rem; }
.lesson-links { display: flex; justify-content: flex-end; gap: 1rem; white-space: nowrap; }
.lesson-links a, .index-footer a { color: var(--green); font-weight: 700; text-decoration: none; }
.lesson-links a:hover, .index-footer a:hover { text-decoration: underline; }
.index-page [hidden] { display: none !important; }
.index-footer { width: 95%; margin: 0 auto; padding: .75rem 0 1.25rem; display: flex; justify-content: space-between; gap: 1rem; color: var(--muted); border-top: 1px solid var(--line); }
@media (max-width: 760px) {
  .index-tools { grid-template-columns: 1fr; gap: .45rem; }
  #search-status { text-align: left; }
  .lesson-row { grid-template-columns: 2.5rem minmax(0, 1fr); gap: .35rem .75rem; }
  .lesson-links { grid-column: 2; justify-content: flex-start; }
  .index-footer { flex-direction: column; gap: .25rem; }
}