:root {
  --ink: #29263a;
  --muted: #817d92;
  --paper: #f7f3ee;
  --card: #fffdf9;
  --purple: #5c4b9b;
  --purple-dark: #40326f;
  --lavender: #e9e3fa;
  --yellow: #e8bb53;
  --line: #ebe5df;
  --success: #3d8b70;
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif; }
button, input { font: inherit; }
button { cursor: pointer; }
.app-shell { width: min(100%, 720px); min-height: 100vh; margin: 0 auto; padding: 22px 18px 94px; }
.topbar, .view-heading, .section-heading { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.topbar { margin-bottom: 24px; }
.eyebrow, .lesson-kicker, .stat-label { color: var(--muted); font-size: 12px; letter-spacing: .08em; margin: 0 0 5px; }
h1, h2, h3, p { margin-top: 0; }
h1 { font-size: 26px; letter-spacing: -.04em; margin-bottom: 0; }
h2 { font-size: clamp(23px, 5vw, 32px); line-height: 1.3; letter-spacing: -.04em; margin-bottom: 10px; }
h3 { font-size: 17px; margin-bottom: 0; }
.icon-button, .back-button { border: 0; background: transparent; color: var(--muted); }
.icon-button { width: 38px; height: 38px; border-radius: 50%; background: var(--card); box-shadow: 0 5px 14px #49347710; font-size: 17px; }
.hero-card { background: linear-gradient(135deg, var(--purple-dark), var(--purple)); color: #fff; border-radius: 24px; padding: 24px 21px; display: flex; justify-content: space-between; align-items: center; gap: 18px; box-shadow: 0 14px 30px #5c4b9b2b; }
.hero-card h2 { font-size: 23px; max-width: 420px; margin: 10px 0 7px; }
.hero-card p { color: #e3ddf4; line-height: 1.6; font-size: 14px; margin-bottom: 0; }
.status-pill { display: inline-flex; color: var(--purple-dark); background: var(--lavender); border-radius: 999px; font-size: 12px; padding: 5px 10px; }
.hero-card .status-pill { background: #ffffff1e; color: #f8f3ff; }
.progress-ring { flex: 0 0 72px; width: 72px; height: 72px; border: 7px solid #ffffff30; border-top-color: var(--yellow); border-right-color: var(--yellow); border-radius: 50%; display: grid; place-items: center; transform: rotate(20deg); }
.progress-ring span { transform: rotate(-20deg); font-weight: 700; font-size: 15px; }
.stats-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 14px 0 18px; }
.stat-card { background: var(--card); border: 1px solid var(--line); padding: 14px 12px; border-radius: 16px; }
.stat-card strong { display: block; font-size: 25px; letter-spacing: -.05em; margin: 3px 0; }
.stat-card small { color: var(--muted); font-size: 12px; }
.primary-button { border: 0; border-radius: 14px; padding: 14px 18px; color: #fff; background: var(--purple); font-weight: 700; box-shadow: 0 8px 18px #5c4b9b25; transition: transform .15s, background .15s; }
.primary-button:hover { background: var(--purple-dark); transform: translateY(-1px); }
.primary-button span { float: right; font-size: 19px; line-height: 16px; }
.full { width: 100%; }
.section-heading { margin: 30px 0 12px; }
.section-heading span, .unit-count { color: var(--muted); font-size: 12px; }
.path-list, .review-list { display: grid; gap: 10px; }
.path-item, .review-item { width: 100%; text-align: left; border: 1px solid var(--line); background: var(--card); border-radius: 16px; padding: 14px 15px; display: flex; align-items: center; gap: 12px; }
.path-item .dot { width: 27px; height: 27px; border-radius: 50%; display: grid; place-items: center; color: var(--purple); background: var(--lavender); font-size: 13px; font-weight: 700; flex: 0 0 auto; }
.path-item.done .dot { color: #fff; background: var(--success); }
.path-item.current { border-color: #b9a9eb; box-shadow: 0 3px 0 #b9a9eb; }
.path-item h4, .review-item h4 { margin: 0 0 4px; font-size: 15px; }
.path-item p, .review-item p { margin: 0; color: var(--muted); font-size: 12px; line-height: 1.5; }
.view { display: none; }
.view.active { display: block; }
.view-heading { margin-bottom: 18px; }
.view-heading h2 { margin: 0; font-size: 23px; }
.back-button { padding: 4px 0; }
.lesson-card, .quiz-card { background: var(--card); border: 1px solid var(--line); border-radius: 22px; padding: 22px 19px; margin-bottom: 14px; }
.lesson-card h2 { font-size: clamp(25px, 6vw, 36px); letter-spacing: .08em; margin: 10px 0 6px; line-height: 1.6; }
.pinyin { color: var(--purple); letter-spacing: .04em; line-height: 1.7; margin-bottom: 5px; font-size: 14px; }
.text-button { border: 0; padding: 2px 0; color: var(--purple); background: transparent; font-size: 12px; }
.meaning-box { background: #f4f0fc; border-radius: 15px; padding: 15px; margin-top: 20px; }
.meaning-box.alt { background: #fbf4e4; }
.meaning-box p { line-height: 1.75; margin: 5px 0 0; font-size: 15px; }
.char-title { margin-top: 21px; }
.char-list { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }
.char-chip { border: 1px solid #ded5f5; background: #f8f5ff; color: var(--purple-dark); border-radius: 11px; padding: 8px 10px; min-width: 54px; }
.char-chip b { font-size: 19px; margin-right: 5px; }
.char-chip small { color: var(--muted); }
.quiz-card h2 { margin-top: 18px; font-size: 24px; }
.quiz-prompt { background: #f8f5ff; border-radius: 14px; padding: 18px; font-size: 22px; letter-spacing: .11em; text-align: center; margin: 18px 0; }
.quiz-input { display: block; width: 100%; border: 1px solid #d9d1ed; background: #fff; border-radius: 12px; padding: 13px 14px; outline: none; margin-bottom: 12px; }
.quiz-input:focus { border-color: var(--purple); box-shadow: 0 0 0 3px #5c4b9b15; }
.feedback { margin-top: 14px; line-height: 1.65; font-size: 14px; }
.feedback.success { color: var(--success); }
.feedback.error { color: #b85b51; }
.review-intro { background: #f1ecfc; border-radius: 16px; padding: 16px; margin-bottom: 15px; }
.review-intro strong { font-size: 16px; }
.review-intro p { margin: 5px 0 0; color: var(--muted); font-size: 13px; }
.review-item { justify-content: space-between; }
.review-item .review-action { flex: 0 0 auto; border: 0; background: var(--lavender); color: var(--purple-dark); border-radius: 10px; padding: 8px 10px; font-size: 12px; }
.char-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; }
.char-card { border: 1px solid var(--line); border-radius: 15px; background: var(--card); padding: 13px; }
.char-card b { font-size: 27px; color: var(--purple-dark); margin-right: 7px; }
.char-card span { font-size: 13px; color: var(--muted); }
.char-card p { margin: 7px 0 0; color: var(--ink); font-size: 13px; line-height: 1.5; }
.bottom-nav { position: fixed; bottom: 0; left: 50%; transform: translateX(-50%); width: min(100%, 720px); display: grid; grid-template-columns: repeat(3, 1fr); background: #fffdf9f2; border-top: 1px solid var(--line); backdrop-filter: blur(12px); padding: 9px 12px max(9px, env(safe-area-inset-bottom)); z-index: 4; }
.nav-item { border: 0; background: transparent; color: var(--muted); font-size: 11px; display: grid; gap: 3px; justify-items: center; }
.nav-item span { font-size: 20px; line-height: 20px; }
.nav-item.active { color: var(--purple); font-weight: 700; }
.toast { position: fixed; left: 50%; bottom: 84px; transform: translateX(-50%) translateY(15px); background: #29263aeb; color: #fff; border-radius: 10px; padding: 10px 15px; font-size: 13px; opacity: 0; pointer-events: none; transition: .2s; z-index: 5; }
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
@media (min-width: 600px) { .app-shell { padding-top: 34px; } .hero-card { padding: 30px; } .stats-grid { gap: 14px; } .lesson-card, .quiz-card { padding: 30px; } }