/* One design system for the whole site (final plan 3.1). Every page uses these variables; no second global stylesheet.
   Colours: 方案 A, Apple's system look (学习体验标准 4.1, owner 2026-10-21): light grey ground, white surfaces, near-black
   text, one blue only for what is chosen, links and the main button. Text and icons keep at least 4.5:1 contrast. */
:root {
  --bg: #F5F5F7;
  --surface: #FFFFFF;
  --text: #1D1D1F;
  --text-muted: #6E6E73;
  --line: #D2D2D7;
  --line-soft: #E5E5EA;
  --primary: #0071E3;
  --primary-hover: #0062C4;
  --link: #0066CC;
  --accent-soft: #E8F1FC;
  --selected-text: #0062C4;  /* text on --accent-soft: 5.2:1 (the brand blue there is 4.1, under 4.5) */
  --hover: #EDEDF0;
  --danger: #B3261E;
  --focus: #0071E3;
  --space-1: 4px; --space-2: 8px; --space-3: 12px; --space-4: 16px; --space-5: 24px; --space-6: 32px; --space-8: 48px;
  --radius: 8px;
  --radius-panel: 12px;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Cascadia Mono", monospace;
}
* { box-sizing: border-box; }
html { font-size: 16px; }
body { margin: 0; background: var(--bg); color: var(--text); font: 1rem/1.65 var(--font); }
a { color: var(--link); }
a:hover { color: var(--primary-hover); }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }
.small, small { font-size: 0.875rem; color: var(--text-muted); }
/* read by screen readers, not shown (e.g. the study header's 位置已保存 next to its tick) */
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }

.site-header { display: flex; align-items: center; justify-content: space-between; gap: var(--space-4);
  padding: var(--space-3) var(--space-5); background: var(--surface); border-bottom: 1px solid var(--line); }
.brand { font-weight: 700; color: var(--text); text-decoration: none; }
.site-header nav { display: flex; align-items: center; gap: var(--space-4); min-width: 0; }
.brand, .site-header nav > *, .site-header nav button { white-space: nowrap; }
.site-header .account-link { display: inline-block; max-width: 14em; overflow: hidden; text-overflow: ellipsis; vertical-align: bottom; }
.env-label { font-size: 0.8125rem; color: var(--text-muted); border: 1px solid var(--line); border-radius: 999px; padding: 0 var(--space-2); }
/* an admin's account menu: the environment (本机) and the account page (学习体验标准 4.2) */
.header-menu { position: relative; }
.header-menu > summary { list-style: none; cursor: pointer; color: var(--link); }
.header-menu > summary::-webkit-details-marker { display: none; }
.header-menu-list { position: absolute; right: 0; top: calc(100% + 6px); z-index: 50; min-width: 12em; margin: 0; padding: 6px; list-style: none;
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12); }
.header-menu-list li { padding: 4px 8px; white-space: nowrap; }
.env-label-row { color: var(--text-muted); border-bottom: 1px solid var(--line-soft); }
/* 紧凑 (学习体验标准第四版 第七节 17 条, 10-22): page titles 20, section and card titles at most 16, buttons and fields at
   most 32 high, margins 12 to 24. Fields keep 16 px text, so a phone does not zoom in when one is tapped. */
main.page { max-width: 1200px; margin: 0 auto; padding: var(--space-5); }
.card { background: var(--surface); border: 1px solid var(--line-soft); border-radius: var(--radius-panel); padding: var(--space-5); }
.narrow { max-width: 420px; margin: var(--space-5) auto; }
h1 { font-size: 1.25rem; line-height: 1.35; margin: 0 0 var(--space-3); }
h2 { font-size: 1rem; margin: 0 0 var(--space-3); }
h3 { font-size: 1rem; }

label { display: block; font-weight: 600; margin: 0 0 var(--space-1); }
input:not([type]), input[type=text], input[type=password], input[type=email], input[type=number], input[type=search], input[type=date],
input[type=tel], input[type=url], select, textarea {
  width: 100%; font: inherit; line-height: 1.25; padding: 5px 10px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); color: var(--text); }
textarea { line-height: 1.5; }
.field { margin: 0 0 var(--space-4); }
.button, button { font: inherit; font-size: 0.875rem; line-height: 1.4; border-radius: var(--radius); padding: 5px 14px; cursor: pointer; border: 1px solid var(--line);
  background: var(--surface); color: var(--text); }
.button.primary, button.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.button.primary:hover, button.primary:hover { background: var(--primary-hover); }
.button.danger, button.danger { color: var(--danger); border-color: var(--danger); background: var(--surface); }
.link-button { border: 0; background: none; padding: 0; color: var(--link); text-decoration: underline; text-underline-offset: 2px; }
.notice { border-radius: var(--radius); padding: var(--space-3) var(--space-4); margin: 0 0 var(--space-4); background: #FFF7E6; border: 1px solid #F1D9A6; }
.error { color: var(--danger); }
.tag { font-size: 0.8125rem; color: var(--text-muted); border: 1px solid var(--line); border-radius: 999px; padding: 0 var(--space-2); white-space: nowrap; }

.course-card { margin: 0 0 var(--space-5); }
.resume-card { display: flex; align-items: center; justify-content: space-between; gap: var(--space-4); margin: 0 0 var(--space-5); border-color: var(--primary); }
.resume-card h2 { margin: 0; }
.resume-card p { margin: 0; }
.course-head { display: flex; align-items: baseline; justify-content: space-between; gap: var(--space-4); }
.part-title { font-size: 1rem; margin: var(--space-4) 0 var(--space-2); color: var(--text-muted); }
.chapter-list { list-style: none; margin: 0; padding: 0; }
.chapter-list li { padding: var(--space-2) 0; border-top: 1px solid var(--line); display: flex; gap: var(--space-3); align-items: baseline; }
.chapter-list li:first-child { border-top: 0; }
/* 我的课程: how far each chapter got, on the right of its row (学习体验标准 四) */
.chapter-list .chapter-status { margin-left: auto; color: var(--text-muted); text-align: right; display: inline-flex; flex-wrap: wrap; gap: var(--space-2);
  align-items: baseline; justify-content: flex-end; }
.tag.done { color: var(--selected-text); border-color: #A9CBF2; background: var(--accent-soft); }

.section-gap { margin: 0 0 var(--space-5); }
.row-list { list-style: none; margin: 0; padding: 0; }
.row-list li { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-3); padding: var(--space-3) 0; border-bottom: 1px solid var(--line); }
.row-list li:last-child { border-bottom: 0; }
/* the first column holds the name: never narrower than 240 px (Chinese breaks anywhere, so a bare flex: 1 let a long
   message beside it squeeze a name to one character per line, decision 39); short of room the row wraps instead */
.row-list li > span:first-child { flex: 1 1 240px; min-width: min(240px, 100%); }
.form-narrow { max-width: 420px; }
.choice-list { border: 0; margin: 0 0 var(--space-4); padding: 0; }
.choice { display: flex; gap: var(--space-3); align-items: flex-start; font-weight: 400; padding: var(--space-3); border: 1px solid var(--line); border-radius: var(--radius); margin: var(--space-2) 0; cursor: pointer; }
.choice input { margin-top: 0.4em; }
.actions { display: flex; gap: var(--space-3); flex-wrap: wrap; }
.narrow.wide-narrow { max-width: 560px; }
.steps { padding-left: 1.25em; }
.steps li { margin: 0 0 var(--space-3); }
/* Two-step QR (学习体验标准 11.21): the bitmap for this screen's density at its own size, never stretched or smoothed */
.qr { margin: var(--space-3) 0 var(--space-1); }
.qr img { display: block; max-width: none; image-rendering: crisp-edges; image-rendering: pixelated; }
.qr-name { margin: 0 0 var(--space-2); }
.recovery-codes { columns: 2; padding-left: 1.5em; font-size: 1.05rem; }
.recovery-codes li { margin: 0 0 var(--space-2); }
code { font-family: var(--mono); }
.site-footer { text-align: center; padding: var(--space-4) var(--space-5) var(--space-6); }
.site-footer .footer-note { margin: 0 0 var(--space-2); }
.prose { max-width: 820px; margin: 0 auto; }
.prose li { margin: 0 0 var(--space-2); }
.prose h2[id] { scroll-margin-top: var(--space-4); }
/* 帮助: the page's own table of contents (普查报告 09) */
.help-toc { display: flex; flex-wrap: wrap; gap: var(--space-1) var(--space-4); margin: 0 0 var(--space-5); padding: var(--space-3) var(--space-4);
  background: var(--bg); border-radius: var(--radius); font-size: 0.9375rem; }
.help-toc a { white-space: nowrap; }
/* sign-in and the short notice pages sit higher, so the footer stays on the first screen at 1366×768 (普查报告 01) */
.card.narrow.compact { margin: var(--space-3) auto var(--space-4); }
.plain-table { width: 100%; border-collapse: collapse; margin: var(--space-3) 0; }
.plain-table th, .plain-table td { border: 1px solid var(--line); padding: var(--space-2) var(--space-3); text-align: left; vertical-align: top; }
.plain-table th { background: var(--bg); }

/* Phones: one header line, less padding (final plan 2.2 rule 6: phones watch and review). */
@media (max-width: 600px) {
  .site-header { padding: var(--space-2) var(--space-4); gap: var(--space-3); }
  .site-header nav { gap: var(--space-3); }
  .site-header .account-link { max-width: 9em; }
  .env-label { display: none; }
  main.page { padding: var(--space-5) var(--space-4); }
  .card { padding: var(--space-4); }
  h1 { font-size: 1.3rem; }
  .resume-card { flex-wrap: wrap; }
}