/* Learning Notes — static bilingual personal space */
:root {
  --bg: #f6f8fd;
  --surface: #ffffff;
  --surface-soft: #eef2fb;
  --ink: #151a2b;
  --ink-2: #3d465e;
  --muted: #6b748c;
  --line: #e2e7f3;
  --brand: #4f46e5;
  --brand-2: #7c3aed;
  --cyan: #06b6d4;
  --radius: 16px;
  --shadow: 0 10px 34px rgba(31, 41, 84, .07);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", "Source Han Sans SC", Arial, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
button { font-family: inherit; }
.wrap { width: min(1080px, calc(100% - 48px)); margin: 0 auto; }

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255, 255, 255, .88);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--line);
}
.header-inner { display: flex; align-items: center; gap: 28px; min-height: 72px; }
.brand { display: flex; align-items: center; gap: 10px; margin-right: auto; min-width: 0; }
.brand-mark {
  display: grid; place-items: center;
  width: 38px; height: 38px; border-radius: 11px;
  color: #fff;
  background: linear-gradient(135deg, var(--brand), var(--brand-2) 55%, var(--cyan));
  box-shadow: 0 6px 16px rgba(79, 70, 229, .28);
}
.brand-name { font-weight: 750; font-size: 17px; letter-spacing: .01em; white-space: nowrap; }
.brand-sub {
  font-size: 12px; color: var(--muted); font-weight: 600;
  padding: 2px 8px; border: 1px solid var(--line); border-radius: 999px;
  background: var(--surface);
}
.site-nav { display: flex; gap: 26px; }
.site-nav a { font-size: 14px; font-weight: 600; color: var(--ink-2); transition: color .18s ease; }
.site-nav a:hover { color: var(--brand); }
.lang-switch {
  display: flex; padding: 3px; gap: 2px;
  background: var(--surface-soft); border: 1px solid var(--line); border-radius: 999px;
}
.lang-btn {
  border: 0; cursor: pointer; background: transparent;
  color: var(--muted); font-size: 13px; font-weight: 700;
  min-width: 38px; height: 28px; border-radius: 999px;
  transition: background .18s ease, color .18s ease, box-shadow .18s ease;
}
.lang-btn.is-active { background: var(--surface); color: var(--brand); box-shadow: 0 2px 6px rgba(31, 41, 84, .12); }

/* ---------- hero ---------- */
.hero { position: relative; overflow: hidden; border-bottom: 1px solid var(--line); background: var(--surface); }
.hero::before {
  content: ""; position: absolute; width: 460px; height: 460px; right: -120px; top: -230px;
  background: radial-gradient(circle, rgba(124, 58, 237, .16), transparent 68%);
}
.hero::after {
  content: ""; position: absolute; width: 380px; height: 380px; left: -160px; bottom: -250px;
  background: radial-gradient(circle, rgba(6, 182, 212, .13), transparent 68%);
}
.hero-inner {
  position: relative; z-index: 1;
  display: grid; grid-template-columns: 1.35fr .8fr; gap: 56px; align-items: center;
  padding-top: 84px; padding-bottom: 88px;
}
.eyebrow { display: inline-flex; align-items: center; gap: 9px; margin: 0 0 22px; font-size: 12px; font-weight: 750; letter-spacing: .14em; color: var(--brand); }
.eyebrow .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 0 4px rgba(6, 182, 212, .15); }
.hero h1 { margin: 0; font-size: clamp(34px, 4.4vw, 54px); line-height: 1.26; font-weight: 800; letter-spacing: -.02em; }
.hero h1 > span { display: block; }
.hero-accent {
  margin-top: 6px;
  background: linear-gradient(100deg, var(--brand), var(--brand-2) 48%, var(--cyan));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero-desc { max-width: 600px; margin: 24px 0 0; color: var(--ink-2); font-size: 16px; line-height: 1.9; }
.hero-tags { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 28px; }
.tag { font-size: 12.5px; font-weight: 650; color: var(--ink-2); background: var(--surface-soft); border: 1px solid var(--line); padding: 5px 13px; border-radius: 999px; }

.hero-art { position: relative; display: grid; place-items: center; min-height: 260px; }
.art-card {
  width: 100%; max-width: 290px; padding: 20px;
  background: var(--surface); border: 1px solid var(--line); border-radius: 18px;
  box-shadow: 0 22px 48px rgba(43, 51, 100, .14);
  transform: rotate(-4deg);
}
.art-top { display: flex; gap: 6px; margin-bottom: 22px; }
.art-top i { width: 8px; height: 8px; border-radius: 50%; background: #e4e8f4; }
.art-top i:first-child { background: #fb7185; }
.art-top i:nth-child(2) { background: #fbbf24; }
.art-top i:nth-child(3) { background: #34d399; }
.art-line { height: 9px; border-radius: 6px; background: linear-gradient(90deg, #e9ecf7, #f3f5fb); margin-bottom: 11px; }
.w90 { width: 90%; } .w80 { width: 80%; } .w70 { width: 70%; } .w60 { width: 60%; }
.art-block { height: 52px; border-radius: 10px; margin: 16px 0; background: linear-gradient(120deg, rgba(79,70,229,.14), rgba(6,182,212,.14)); }
.art-badge {
  position: absolute; right: -4px; bottom: 18px;
  padding: 9px 16px; border-radius: 12px; color: #fff; font-size: 12px; font-weight: 750; letter-spacing: .08em;
  background: linear-gradient(120deg, var(--brand), var(--brand-2));
  box-shadow: 0 12px 24px rgba(79, 70, 229, .3);
  transform: rotate(5deg);
}

/* ---------- sections ---------- */
.section { padding: 76px 0; }
.section-soft { background: var(--surface-soft); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.section-head { display: flex; align-items: end; justify-content: space-between; gap: 30px; margin-bottom: 34px; }
.section-kicker { margin: 0 0 8px; font-size: 12px; font-weight: 750; letter-spacing: .15em; color: var(--brand); }
.section h2 { margin: 0; font-size: clamp(24px, 2.6vw, 32px); font-weight: 780; letter-spacing: -.01em; }
.section-note { margin: 0; color: var(--muted); font-size: 13.5px; max-width: 300px; text-align: right; }

.cards { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 20px; }
.card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 26px 26px 20px; box-shadow: var(--shadow);
  transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease;
}
.card:hover { transform: translateY(-3px); box-shadow: 0 16px 40px rgba(31, 41, 84, .11); border-color: #cfd7ef; }
.card-meta { display: flex; align-items: center; gap: 12px; margin-bottom: 14px; }
.card-meta time { font-size: 12.5px; color: var(--muted); font-variant-numeric: tabular-nums; }
.chip { font-size: 11.5px; font-weight: 700; color: var(--brand); background: rgba(79, 70, 229, .09); padding: 3px 10px; border-radius: 999px; }
.card h3 { margin: 0 0 10px; font-size: 19px; font-weight: 720; line-height: 1.45; }
.card > p { margin: 0; color: var(--ink-2); font-size: 14.5px; line-height: 1.8; }
.card details { margin-top: 18px; border-top: 1px dashed var(--line); padding-top: 14px; }
.card summary { cursor: pointer; font-size: 13.5px; font-weight: 680; color: var(--brand); list-style: none; }
.card summary::-webkit-details-marker { display: none; }
.card summary::before { content: "+"; display: inline-block; width: 18px; font-weight: 800; }
.card details[open] summary::before { content: "−"; }
.card ul { margin: 12px 0 2px; padding-left: 20px; color: var(--ink-2); font-size: 13.5px; line-height: 1.85; }
.card li { margin-bottom: 5px; }

.about-grid { display: grid; grid-template-columns: .85fr 1.4fr; gap: 54px; }
.about-body p { margin: 0 0 16px; color: var(--ink-2); line-height: 1.9; }
.notice {
  display: flex; align-items: flex-start; gap: 12px; margin-top: 22px;
  padding: 15px 18px; border-radius: 12px; font-size: 14px; font-weight: 600; color: var(--ink-2);
  background: var(--surface); border: 1px solid #dbe2f6;
}
.notice-icon {
  flex: none; display: grid; place-items: center; width: 21px; height: 21px; border-radius: 50%;
  color: #fff; background: var(--brand); font-size: 12px; font-style: italic; font-family: Georgia, serif; font-weight: 700;
}

.info-table { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); }
.info-row { display: grid; grid-template-columns: 230px 1fr; border-bottom: 1px solid var(--line); }
.info-row:last-child { border-bottom: 0; }
.info-key, .info-val { padding: 15px 24px; font-size: 14.5px; }
.info-key { background: #fafbff; color: var(--muted); font-weight: 650; border-right: 1px solid var(--line); }
.info-val { color: var(--ink); font-weight: 560; }
.mono { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; letter-spacing: .02em; }
.site-name { color: var(--brand); font-weight: 750; }

/* ---------- footer ---------- */
.site-footer { background: #12182c; color: #c7cee0; }
.footer-inner { padding: 52px 0 26px; }
.footer-top { display: flex; align-items: start; justify-content: space-between; gap: 30px; padding-bottom: 30px; }
.footer-brand { display: flex; flex-direction: column; gap: 5px; }
.footer-brand strong { color: #fff; font-size: 19px; font-weight: 750; }
.footer-brand span { font-size: 13.5px; color: #98a2bd; }
.footer-links { display: flex; gap: 22px; }
.footer-links a { font-size: 13.5px; color: #aeb7cf; }
.footer-links a:hover { color: #fff; }

.beian-bar {
  display: flex; flex-wrap: wrap; gap: 14px;
  padding: 20px; border-radius: 14px;
  background: rgba(255, 255, 255, .055); border: 1px solid rgba(255, 255, 255, .1);
}
.beian-item {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 9px 16px; border-radius: 9px;
  background: rgba(255, 255, 255, .07); border: 1px solid rgba(255, 255, 255, .12);
  transition: background .18s ease, border-color .18s ease;
}
.beian-item:hover { background: rgba(255, 255, 255, .13); border-color: rgba(255, 255, 255, .28); }
.beian-label { font-size: 12px; color: #9aa5c0; font-weight: 600; }
.beian-num { font-size: 14px; color: #ffffff; font-weight: 700; letter-spacing: .01em; }
.beian-shield { color: #8ab4ff; flex: none; }

.footer-bottom {
  display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 12px;
  margin-top: 26px; padding-top: 20px; border-top: 1px solid rgba(255, 255, 255, .09);
  font-size: 12.5px; color: #8993ae;
}
.footer-remark { color: #a9b3cb; }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .hero-inner { grid-template-columns: 1fr; gap: 36px; padding-top: 60px; padding-bottom: 62px; }
  .hero-art { min-height: 0; justify-items: start; }
  .art-card { max-width: 240px; }
  .art-badge { right: auto; left: 190px; bottom: -6px; }
  .about-grid { grid-template-columns: 1fr; gap: 24px; }
  .section-note { text-align: left; }
}
@media (max-width: 680px) {
  .wrap { width: min(100% - 32px, 1080px); }
  .header-inner { gap: 12px; min-height: 64px; flex-wrap: wrap; }
  .brand-sub { display: none; }
  .brand-name { font-size: 15px; }
  .site-nav { display: none; }
  .cards { grid-template-columns: 1fr; }
  .section { padding: 56px 0; }
  .section-head { flex-direction: column; align-items: start; gap: 10px; }
  .info-row { grid-template-columns: 1fr; }
  .info-key { border-right: 0; border-bottom: 1px solid var(--line); padding: 11px 18px; }
  .info-val { padding: 11px 18px; }
  .footer-top { flex-direction: column; gap: 18px; }
  .beian-bar { flex-direction: column; }
  .beian-item { width: 100%; flex-wrap: wrap; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}