/* PrepLingo · Brand Design System
   Tokens 来自 PrepLingo_品牌设计方案.md */

:root {
  /* 品牌主色 */
  --pl-ink:        #1B3A5B;
  --pl-green:      #1D9E75;
  --pl-amber:      #EF9F27;

  /* 绿色色阶 */
  --pl-green-50:   #E1F5EE;
  --pl-green-100:  #9FE1CB;
  --pl-green-200:  #5DCAA5;
  --pl-green-600:  #0F6E56;
  --pl-green-900:  #04342C;

  /* 深蓝色阶 */
  --pl-ink-50:     #E6EDF4;
  --pl-ink-100:    #B5C8DC;
  --pl-ink-500:    #36597D;
  --pl-ink-900:    #0E2138;

  /* 中性色 */
  --pl-bg:         #F7F8FA;
  --pl-surface:    #FFFFFF;
  --pl-text:       #1B3A5B;
  --pl-text-soft:  #5A6B7B;
  --pl-border:     #E2E6EB;

  /* 语义色 */
  --pl-correct:    #1D9E75;
  --pl-wrong:      #E24B4A;
  --pl-warning:    #EF9F27;

  /* 形状 */
  --pl-radius-card: 12px;
  --pl-radius-ctl:  8px;
  --pl-shadow-sm:   0 1px 2px rgba(14, 33, 56, .04), 0 1px 1px rgba(14, 33, 56, .03);
  --pl-shadow-md:   0 4px 16px rgba(14, 33, 56, .08), 0 1px 3px rgba(14, 33, 56, .05);

  /* 字体 */
  --pl-font: "Inter", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --pl-bg:        #0E2138;
    --pl-surface:   #1B3A5B;
    --pl-text:      #FFFFFF;
    --pl-text-soft: #B5C8DC;
    --pl-border:    #36597D;
    --pl-green:     #5DCAA5;
    --pl-ink:       #FFFFFF;
    --pl-ink-50:    #1B3A5B;
  }
}

/* ---------- Reset / Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--pl-font);
  font-weight: 400;
  font-size: 16px;
  line-height: 1.6;
  color: var(--pl-text);
  background: var(--pl-bg);
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3, h4 {
  font-weight: 500;
  letter-spacing: -0.01em;
  line-height: 1.25;
  margin: 0 0 .6em;
  color: var(--pl-text);
}
h1 { font-size: clamp(1.8rem, 1.2rem + 2vw, 2.6rem); }
h2 { font-size: clamp(1.4rem, 1.1rem + 1vw, 1.8rem); }
h3 { font-size: 1.18rem; }
p { margin: 0 0 1em; }
a {
  color: var(--pl-green);
  text-decoration: none;
}
a:hover { text-decoration: underline; }
ul { padding-left: 1.2em; }
hr { border: 0; border-top: 1px solid var(--pl-border); margin: 2rem 0; }

.skip-link {
  position: absolute; left: -9999px; top: 0;
  background: var(--pl-ink); color: #fff; padding: .5rem 1rem; z-index: 99;
}
.skip-link:focus { left: 1rem; top: 1rem; }

.container {
  width: 100%;
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* ---------- Header / Nav ---------- */
.site-header {
  background: var(--pl-surface);
  border-bottom: 1px solid var(--pl-border);
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: saturate(180%) blur(8px);
}
.nav-row {
  display: flex; align-items: center; justify-content: space-between;
  min-height: 64px; gap: 1rem;
}
.brand {
  display: inline-flex; align-items: center; gap: .55rem;
  text-decoration: none; color: var(--pl-ink);
  font-weight: 500; font-size: 1.18rem;
  letter-spacing: -0.5px;
}
.brand:hover { text-decoration: none; }
.brand-mark { color: var(--pl-ink); display: inline-flex; }
.brand-text .brand-prep { color: var(--pl-ink); }
.brand-text .brand-lingo { color: var(--pl-green); }

.primary-nav {
  display: flex; gap: .25rem; flex-wrap: wrap;
}
.primary-nav a {
  color: var(--pl-text-soft);
  padding: .5rem .75rem;
  border-radius: var(--pl-radius-ctl);
  font-weight: 500; font-size: .95rem;
}
.primary-nav a:hover { color: var(--pl-ink); background: var(--pl-ink-50); text-decoration: none; }
.primary-nav a.active { color: var(--pl-green); background: var(--pl-green-50); }

.nav-toggle {
  display: none; background: transparent; border: 0; padding: .5rem;
  cursor: pointer;
}
.nav-toggle span {
  display: block; width: 24px; height: 2px;
  background: var(--pl-ink); margin: 5px 0; border-radius: 2px;
  transition: transform .2s ease, opacity .2s ease;
}

@media (max-width: 820px) {
  .nav-toggle { display: block; }
  .primary-nav {
    position: absolute; top: 64px; left: 0; right: 0;
    background: var(--pl-surface);
    border-bottom: 1px solid var(--pl-border);
    padding: .5rem 1.25rem 1rem;
    flex-direction: column; align-items: stretch;
    gap: 0;
    display: none;
  }
  .primary-nav.open { display: flex; }
  .primary-nav a { padding: .75rem .5rem; border-bottom: 1px solid var(--pl-border); border-radius: 0; }
  .primary-nav a:last-child { border-bottom: 0; }
}

/* ---------- Layout ---------- */
.app-main { padding: 2rem 1.25rem 4rem; min-height: 60vh; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; gap: .5rem;
  font-family: inherit; font-weight: 500; font-size: .95rem;
  padding: .65rem 1.1rem;
  border-radius: var(--pl-radius-ctl);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background .15s ease, border-color .15s ease, color .15s ease, transform .05s ease;
  text-decoration: none;
  line-height: 1;
}
.btn:active { transform: translateY(1px); }
.btn:focus-visible { outline: 2px solid var(--pl-green); outline-offset: 2px; }
.btn-primary {
  background: var(--pl-green); color: #fff;
}
.btn-primary:hover { background: var(--pl-green-600); color: #fff; text-decoration: none; }
.btn-secondary {
  background: transparent; color: var(--pl-ink);
  border-color: var(--pl-ink);
}
.btn-secondary:hover { background: var(--pl-ink-50); }
.btn-ghost {
  background: transparent; color: var(--pl-text-soft); border-color: var(--pl-border);
}
.btn-ghost:hover { color: var(--pl-ink); border-color: var(--pl-ink); }
.btn-sm { padding: .4rem .7rem; font-size: .85rem; }
.btn-icon {
  width: 38px; height: 38px; padding: 0; justify-content: center;
}

/* ---------- Cards ---------- */
.card {
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 1.25rem;
  box-shadow: var(--pl-shadow-sm);
}
.card + .card { margin-top: 1rem; }

.grid { display: grid; gap: 1rem; }
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }

/* ---------- Form ---------- */
input[type=text], input[type=email], input[type=number], input[type=date], select, textarea {
  font-family: inherit; font-size: 1rem;
  padding: .6rem .8rem;
  border-radius: var(--pl-radius-ctl);
  border: 1px solid var(--pl-border);
  background: var(--pl-surface);
  color: var(--pl-text);
  width: 100%;
}
input:focus, select:focus, textarea:focus {
  outline: none; border-color: var(--pl-green);
  box-shadow: 0 0 0 3px var(--pl-green-50);
}
label { font-size: .9rem; color: var(--pl-text-soft); font-weight: 500; }
.field { display: flex; flex-direction: column; gap: .35rem; margin-bottom: .8rem; }
.row { display: flex; gap: .75rem; flex-wrap: wrap; align-items: center; }

/* ---------- Tags / Badges ---------- */
.tag {
  display: inline-block;
  background: var(--pl-ink-50);
  color: var(--pl-ink);
  font-size: .75rem;
  font-weight: 500;
  padding: .2rem .55rem;
  border-radius: 999px;
  margin-right: .35rem;
  letter-spacing: .02em;
}
.tag-green { background: var(--pl-green-50); color: var(--pl-green-600); }
.tag-amber { background: #FDEFD3; color: #8B5A0F; }
.tag-l1 { background: var(--pl-green-50); color: var(--pl-green-600); }
.tag-l2 { background: #FDEFD3; color: #8B5A0F; }
.tag-l3 { background: #FBE0E0; color: #9B2C2C; }

/* ---------- Hero ---------- */
.hero {
  text-align: left;
  padding: 2rem 0 1rem;
}
.hero h1 { max-width: 22ch; }
.hero p.lede {
  font-size: 1.1rem; color: var(--pl-text-soft); max-width: 60ch;
}
.hero-ctas { display: flex; gap: .75rem; margin-top: 1.25rem; flex-wrap: wrap; }
.hero-stats {
  display: flex; gap: 2rem; margin-top: 2rem; flex-wrap: wrap;
  color: var(--pl-text-soft); font-size: .9rem;
}
.hero-stats strong {
  display: block; color: var(--pl-ink); font-size: 1.4rem; font-weight: 500;
  letter-spacing: -.02em;
}

/* ---------- Feature grid ---------- */
.feature-card {
  display: flex; flex-direction: column; gap: .5rem;
  text-decoration: none; color: inherit;
  transition: transform .15s ease, box-shadow .15s ease, border-color .15s ease;
}
.feature-card:hover {
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: var(--pl-shadow-md);
  border-color: var(--pl-green-100);
}
.feature-icon {
  width: 44px; height: 44px; border-radius: 10px;
  background: var(--pl-green-50); color: var(--pl-green-600);
  display: inline-flex; align-items: center; justify-content: center;
  margin-bottom: .25rem;
  font-weight: 600;
}
.feature-card h3 { margin: 0 0 .25rem; }
.feature-card p { color: var(--pl-text-soft); font-size: .92rem; margin: 0; }

/* ---------- Page header ---------- */
.page-head {
  display: flex; align-items: flex-end; justify-content: space-between;
  flex-wrap: wrap; gap: 1rem; margin-bottom: 1.25rem;
}
.page-head .crumbs { color: var(--pl-text-soft); font-size: .85rem; }
.page-head h1 { margin: .25rem 0 .25rem; }
.page-head p { color: var(--pl-text-soft); margin: 0; }

/* ---------- Word / Vocab ---------- */
.toolbar {
  display: flex; gap: .5rem; flex-wrap: wrap;
  padding: 0.85rem 1rem;
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  margin-bottom: 1rem;
  align-items: center;
}
.toolbar select { width: auto; min-width: 130px; }
.toolbar .spacer { flex: 1; }
.search-input {
  min-width: 180px;
}

.vocab-list { display: grid; gap: .75rem; }
.vocab-row {
  background: var(--pl-surface); border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 1rem 1.1rem;
  display: grid; gap: .35rem;
  grid-template-columns: 1fr auto;
  align-items: start;
}
.vocab-row .term {
  font-size: 1.15rem; font-weight: 500;
  color: var(--pl-ink);
}
.vocab-row .phonetic { color: var(--pl-text-soft); font-style: italic; margin-left: .5rem; font-size: .92rem; }
.vocab-row .def { color: var(--pl-text); font-size: .95rem; }
.vocab-row .ex {
  color: var(--pl-text-soft); font-size: .9rem; font-style: italic;
  border-left: 3px solid var(--pl-green-100); padding-left: .75rem; margin-top: .25rem;
}
.vocab-row .actions { display: flex; gap: .35rem; align-items: center; }
.vocab-row.mastered { opacity: .6; }
.vocab-row.mastered .term::after { content: " ✓"; color: var(--pl-green); }

/* ---------- Dictation / Practice ---------- */
.practice-stage {
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 2rem 1.5rem;
  text-align: center;
  margin-bottom: 1rem;
  box-shadow: var(--pl-shadow-sm);
}
.practice-stage .prompt {
  color: var(--pl-text-soft);
  font-size: .92rem;
  text-transform: uppercase;
  letter-spacing: .08em;
  margin-bottom: .75rem;
}
.practice-stage .big-text {
  font-size: clamp(1.2rem, 1rem + 1vw, 1.6rem);
  color: var(--pl-ink);
  font-weight: 500;
  margin: .75rem 0 1rem;
  min-height: 2.4em;
}
.practice-controls {
  display: flex; gap: .5rem; justify-content: center; flex-wrap: wrap;
  margin: 1rem 0;
}
.input-answer {
  font-size: 1.1rem;
  text-align: center;
  max-width: 420px;
  margin: 0 auto;
}
.feedback {
  margin-top: 1rem;
  padding: .85rem 1rem;
  border-radius: var(--pl-radius-ctl);
  font-weight: 500;
  display: none;
}
.feedback.correct { display: block; background: var(--pl-green-50); color: var(--pl-green-600); }
.feedback.wrong { display: block; background: #FDECEC; color: #9B2C2C; }
.feedback .icon { margin-right: .35rem; font-weight: 600; }

.diff-line {
  font-size: 1.05rem; line-height: 1.7;
  margin: .5rem 0;
}
.diff-line .ok { color: var(--pl-green-600); }
.diff-line .bad { color: var(--pl-wrong); text-decoration: line-through; }
.diff-line .miss { color: var(--pl-wrong); background: #FBE0E0; border-radius: 3px; padding: 0 .25rem; }
.diff-line .extra { color: var(--pl-warning); }

/* Cloze blanks */
.cloze-line { font-size: 1.15rem; line-height: 2; color: var(--pl-ink); }
.cloze-blank {
  display: inline-block;
  border: 0; border-bottom: 2px solid var(--pl-green);
  background: transparent;
  font: inherit;
  color: var(--pl-ink);
  text-align: center;
  min-width: 110px;
  padding: 0 .25rem;
  margin: 0 .15rem;
}
.cloze-blank:focus { outline: none; background: var(--pl-green-50); }
.cloze-blank.correct { color: var(--pl-correct); border-bottom-color: var(--pl-correct); }
.cloze-blank.wrong { color: var(--pl-wrong); border-bottom-color: var(--pl-wrong); }

/* Progress */
.progress {
  height: 8px; background: var(--pl-ink-50); border-radius: 999px; overflow: hidden;
  margin: .25rem 0;
}
.progress > span {
  display: block; height: 100%; background: var(--pl-amber);
  border-radius: 999px; transition: width .3s ease;
}
.progress.done > span { background: var(--pl-green); }
.session-meta {
  display: flex; justify-content: space-between; font-size: .88rem; color: var(--pl-text-soft);
  margin-bottom: .5rem;
}

/* ---------- Score Converter Table ---------- */
.score-table {
  width: 100%; border-collapse: collapse;
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  overflow: hidden;
}
.score-table th, .score-table td {
  padding: .7rem .8rem; text-align: center;
  border-bottom: 1px solid var(--pl-border);
  font-size: .92rem;
}
.score-table th {
  background: var(--pl-ink); color: #fff;
  font-weight: 500;
}
.score-table tr:last-child td { border-bottom: 0; }
.score-table tr.hl td { background: var(--pl-green-50); font-weight: 500; color: var(--pl-green-600); }

.converter-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  margin-bottom: 1.5rem;
}
.converter-box {
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 1rem;
}
.converter-box label { display: block; margin-bottom: .35rem; }
.converter-box .result {
  font-size: 1.4rem; color: var(--pl-ink); font-weight: 500; margin-top: .3rem;
}

/* ---------- Plan / SRS dashboard ---------- */
.stat-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  margin-bottom: 1.5rem;
}
.stat {
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 1rem;
}
.stat .num {
  font-size: 1.8rem; font-weight: 500; color: var(--pl-ink); letter-spacing: -.02em;
}
.stat .label { font-size: .85rem; color: var(--pl-text-soft); }

.plan-day {
  background: var(--pl-surface);
  border: 1px solid var(--pl-border);
  border-radius: var(--pl-radius-card);
  padding: 1rem;
  margin-bottom: .75rem;
  display: grid; gap: .35rem;
  grid-template-columns: auto 1fr auto;
  align-items: center;
}
.plan-day .day-num {
  width: 40px; height: 40px; border-radius: 50%;
  background: var(--pl-green-50); color: var(--pl-green-600);
  display: inline-flex; align-items: center; justify-content: center;
  font-weight: 600;
}
.plan-day.today .day-num { background: var(--pl-amber); color: #fff; }
.plan-day.done .day-num { background: var(--pl-green); color: #fff; }

/* ---------- Footer ---------- */
.site-footer {
  background: var(--pl-ink);
  color: #B5C8DC;
  padding: 2.5rem 0 1rem;
  margin-top: 3rem;
}
.site-footer h4 { color: #fff; font-size: 1rem; margin-bottom: .75rem; }
.site-footer a { color: #9FE1CB; }
.site-footer a:hover { color: #fff; }
.footer-grid {
  display: grid; gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  margin-bottom: 1.5rem;
}
.footer-grid ul { list-style: none; padding: 0; }
.footer-grid li { margin: .3rem 0; }
.footer-tag { color: #9FE1CB; font-size: .9rem; margin-top: .5rem; }
.footer-disc { font-size: .82rem; color: #B5C8DC; line-height: 1.5; }
.brand--footer { color: #fff; }
.brand--footer .brand-mark { color: #5DCAA5; }
.footer-bottom {
  border-top: 1px solid #36597D;
  padding-top: 1rem;
  font-size: .82rem; color: #B5C8DC;
  text-align: center;
}

/* ---------- Misc ---------- */
.empty {
  text-align: center; padding: 3rem 1rem; color: var(--pl-text-soft);
}
.empty .big { font-size: 2.5rem; opacity: .4; margin-bottom: .5rem; }
.muted { color: var(--pl-text-soft); }
.kbd {
  display: inline-block; padding: 1px 6px;
  border: 1px solid var(--pl-border); border-radius: 4px;
  background: var(--pl-bg); font-family: ui-monospace, monospace; font-size: .8rem;
}

/* prose article */
.prose { max-width: 70ch; }
.prose h2 { margin-top: 2rem; }
.prose h3 { margin-top: 1.5rem; }
.prose ul li { margin-bottom: .35rem; }

/* Print + reduced motion */
@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}