/* =========================================================
   Učím se česky — stylesheet
   Clean, minimal, calm. Soft neutrals + warm accent.
   ========================================================= */

/* ---------- Design Tokens ---------- */
:root {
  /* Surface colors — warm off-white palette */
  --bg:          #f7f4ef;
  --surface:     #ffffff;
  --surface-2:   #f1ece4;
  --border:      #e8e2d6;
  --border-strong: #d8d0bf;

  /* Text */
  --text:        #2a2722;
  --text-muted:  #6b6557;
  --text-soft:   #8e8775;

  /* Accent — muted terracotta, distinctly Czech-flag-adjacent without being literal */
  --accent:      #b04a3a;
  --accent-soft: #e8d5cf;
  --accent-ink:  #8a3528;

  /* Success / wrong feedback */
  --ok:          #4f7a4a;
  --ok-soft:     #dce7d9;
  --err:         #b04a3a;
  --err-soft:    #f0dcd7;

  /* Shape */
  --radius-sm:   8px;
  --radius:      14px;
  --radius-lg:   20px;

  /* Shadow */
  --shadow-sm:   0 1px 2px rgba(40, 30, 20, 0.04), 0 1px 1px rgba(40, 30, 20, 0.03);
  --shadow:      0 4px 16px rgba(40, 30, 20, 0.05), 0 1px 2px rgba(40, 30, 20, 0.04);
  --shadow-lg:   0 12px 40px rgba(40, 30, 20, 0.08);

  /* Type */
  --font-display: 'Fraunces', Georgia, 'Times New Roman', serif;
  --font-body:    'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

  /* Motion */
  --ease:        cubic-bezier(0.4, 0, 0.2, 1);
  --t-fast:      150ms;
  --t-med:       260ms;
}

/* Dark theme */
[data-theme="dark"] {
  --bg:          #1c1a17;
  --surface:     #25221e;
  --surface-2:   #2d2925;
  --border:      #38332d;
  --border-strong: #4a4439;

  --text:        #ece6d9;
  --text-muted:  #9c9588;
  --text-soft:   #7a7466;

  --accent:      #d97a68;
  --accent-soft: #3a2722;
  --accent-ink:  #f0a695;

  --ok:          #8ab285;
  --ok-soft:     #2a352a;
  --err:         #d97a68;
  --err-soft:    #3a2722;

  --shadow-sm:   0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow:      0 4px 16px rgba(0, 0, 0, 0.3);
  --shadow-lg:   0 12px 40px rgba(0, 0, 0, 0.4);
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background var(--t-med) var(--ease), color var(--t-med) var(--ease);
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
}

input { font-family: inherit; }

/* ---------- Header ---------- */
.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 85%, transparent);
  backdrop-filter: saturate(140%) blur(12px);
  -webkit-backdrop-filter: saturate(140%) blur(12px);
  border-bottom: 1px solid var(--border);
}

.header__inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  gap: 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text);
  flex-shrink: 0;
}

.brand__mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 20px;
  line-height: 1;
}

.brand__text {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 18px;
  letter-spacing: -0.01em;
}

.nav {
  display: flex;
  gap: 4px;
  margin-left: auto;
  margin-right: 8px;
  flex-wrap: wrap;
}

.nav__link {
  padding: 8px 14px;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-muted);
  border-radius: 999px;
  transition: all var(--t-fast) var(--ease);
  white-space: nowrap;
}

.nav__link:hover {
  color: var(--text);
  background: var(--surface-2);
}

.nav__link.active {
  background: var(--text);
  color: var(--bg);
}

/* Theme toggle */
.theme-toggle {
  width: 38px;
  height: 38px;
  border-radius: 999px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  transition: all var(--t-fast) var(--ease);
}

.theme-toggle:hover {
  background: var(--surface-2);
  color: var(--text);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

.icon-moon { display: none; }
[data-theme="dark"] .icon-sun { display: none; }
[data-theme="dark"] .icon-moon { display: block; }

/* ---------- Main / Sections ---------- */
.main {
  flex: 1;
  max-width: 1100px;
  width: 100%;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

.section {
  display: none;
  animation: fadeUp var(--t-med) var(--ease);
}

.section.active {
  display: block;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.section__head {
  margin-bottom: 32px;
  max-width: 640px;
}

.eyebrow {
  font-size: 13px;
  font-weight: 500;
  color: var(--accent);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 8px;
}

.section__title {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: clamp(2rem, 4vw, 2.75rem);
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}

.section__lede {
  font-size: 17px;
  color: var(--text-muted);
}

/* ---------- Cards ---------- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow-sm);
}

/* ---------- Chips (category pills) ---------- */
.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 28px;
}

.chip {
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  transition: all var(--t-fast) var(--ease);
}

.chip:hover {
  color: var(--text);
  border-color: var(--border-strong);
}

.chip.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

/* ---------- Buttons ---------- */
.btn {
  padding: 10px 18px;
  font-size: 14px;
  font-weight: 500;
  border-radius: 10px;
  transition: all var(--t-fast) var(--ease);
  white-space: nowrap;
}

.btn--primary {
  background: var(--text);
  color: var(--bg);
}

.btn--primary:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow);
}

.btn--ghost {
  color: var(--text-muted);
  background: var(--surface-2);
}

.btn--ghost:hover {
  color: var(--text);
  background: var(--border);
}

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

/* ---------- Flashcard ---------- */
.flashcard {
  max-width: 640px;
  margin: 0 auto;
  text-align: center;
}

.flashcard__progress {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 13px;
  color: var(--text-soft);
  margin-bottom: 24px;
  font-variant-numeric: tabular-nums;
}

.progress-bar {
  flex: 1;
  height: 4px;
  background: var(--surface-2);
  border-radius: 999px;
  overflow: hidden;
}

.progress-bar__fill {
  height: 100%;
  background: var(--accent);
  border-radius: 999px;
  transition: width var(--t-med) var(--ease);
  width: 0%;
}

.flashcard__body {
  padding: 40px 16px;
  min-height: 200px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.flashcard__czech {
  font-family: var(--font-display);
  font-size: clamp(2.25rem, 6vw, 3.25rem);
  font-weight: 500;
  letter-spacing: -0.02em;
  line-height: 1.1;
}

.flashcard__hint {
  font-size: 14px;
  color: var(--text-soft);
  margin-top: 12px;
  font-style: italic;
}

.flashcard__english {
  font-size: 22px;
  color: var(--text-muted);
  margin-top: 24px;
  animation: fadeUp var(--t-fast) var(--ease);
}

.flashcard__actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 16px;
}

.kbd-hint {
  font-size: 12px;
  color: var(--text-soft);
  margin-top: 16px;
}

/* ---------- Letter Grid (pronunciation) ---------- */
.letter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 12px;
  margin-bottom: 28px;
}

.letter-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  cursor: pointer;
  transition: all var(--t-fast) var(--ease);
  text-align: left;
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-height: 100px;
}

.letter-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.letter-card.expanded {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.letter-card__char {
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 500;
  line-height: 1;
  color: var(--accent);
}

.letter-card__example {
  font-size: 14px;
  color: var(--text-muted);
  font-style: italic;
}

.letter-card__detail {
  display: none;
  font-size: 13px;
  color: var(--text);
  margin-top: 8px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
  line-height: 1.5;
}

.letter-card.expanded .letter-card__detail {
  display: block;
  animation: fadeUp var(--t-fast) var(--ease);
}

.hint-card {
  background: var(--surface-2);
  border-style: dashed;
  max-width: 640px;
}

.hint-card h3 {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 18px;
  margin-bottom: 8px;
}

.hint-card p {
  color: var(--text-muted);
  font-size: 15px;
}

/* ---------- Phrase List ---------- */
.phrase-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.phrase {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: border-color var(--t-fast) var(--ease);
}

.phrase:hover { border-color: var(--border-strong); }

.phrase__header {
  width: 100%;
  text-align: left;
  padding: 18px 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  transition: background var(--t-fast) var(--ease);
}

.phrase__header:hover { background: var(--surface-2); }

.phrase__czech {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 19px;
  letter-spacing: -0.01em;
}

.phrase__english-preview {
  font-size: 14px;
  color: var(--text-soft);
  flex: 1;
  text-align: right;
  font-style: italic;
}

.phrase__chevron {
  width: 16px;
  height: 16px;
  color: var(--text-soft);
  transition: transform var(--t-fast) var(--ease);
  flex-shrink: 0;
}

.phrase.open .phrase__chevron { transform: rotate(180deg); }

.phrase__body {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--t-med) var(--ease);
}

.phrase.open .phrase__body { max-height: 200px; }

.phrase__body-inner {
  padding: 0 22px 20px;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 8px 16px;
  font-size: 14px;
}

.phrase__label {
  color: var(--text-soft);
  font-weight: 500;
}

.phrase__value { color: var(--text); }

.phrase__value--pronunciation {
  font-style: italic;
  color: var(--text-muted);
}

/* ---------- Verb section ---------- */
.verb-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.verb-table h2 {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 28px;
  margin-bottom: 4px;
  letter-spacing: -0.02em;
}

.verb-table__meaning {
  color: var(--text-muted);
  font-size: 14px;
  margin-bottom: 24px;
  font-style: italic;
}

.verb-table table {
  width: 100%;
  border-collapse: collapse;
}

.verb-table td {
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  font-size: 16px;
}

.verb-table tr:last-child td { border-bottom: none; }

.verb-table .pronoun {
  color: var(--text-soft);
  font-size: 14px;
  width: 40%;
  font-style: italic;
}

.verb-table .form {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 18px;
  text-align: right;
}

/* Quiz */
.quiz h3 {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 22px;
  margin-bottom: 16px;
  letter-spacing: -0.01em;
}

.quiz__prompt {
  font-size: 17px;
  color: var(--text-muted);
  margin-bottom: 14px;
  line-height: 1.5;
}

.quiz__prompt strong {
  color: var(--text);
  font-weight: 500;
  font-family: var(--font-display);
  font-size: 22px;
}

.quiz__input {
  width: 100%;
  padding: 12px 14px;
  font-size: 16px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text);
  outline: none;
  transition: all var(--t-fast) var(--ease);
}

.quiz__input:focus {
  border-color: var(--accent);
  background: var(--surface);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.quiz__actions {
  display: flex;
  gap: 8px;
  margin-top: 12px;
}

.quiz__feedback {
  margin-top: 14px;
  padding: 10px 14px;
  border-radius: 10px;
  font-size: 14px;
  min-height: 0;
  opacity: 0;
  transition: opacity var(--t-fast) var(--ease);
}

.quiz__feedback.show { opacity: 1; }

.quiz__feedback.ok {
  background: var(--ok-soft);
  color: var(--ok);
}

.quiz__feedback.err {
  background: var(--err-soft);
  color: var(--err);
}

.quiz__score {
  margin-top: 16px;
  font-size: 13px;
  color: var(--text-soft);
}

.quiz__score span {
  color: var(--text);
  font-weight: 500;
  font-variant-numeric: tabular-nums;
}

/* ---------- Footer ---------- */
.footer {
  border-top: 1px solid var(--border);
  padding: 24px;
  text-align: center;
  font-size: 13px;
  color: var(--text-soft);
}

/* ---------- Responsive ---------- */
@media (max-width: 760px) {
  .header__inner {
    padding: 12px 16px;
    gap: 12px;
    flex-wrap: wrap;
  }

  .brand__text { display: none; }

  .nav {
    order: 3;
    width: 100%;
    margin: 0;
    justify-content: flex-start;
    overflow-x: auto;
    padding-bottom: 4px;
    -webkit-overflow-scrolling: touch;
  }

  .nav::-webkit-scrollbar { display: none; }

  .main { padding: 32px 16px 60px; }

  .card { padding: 24px 20px; }

  .verb-layout { grid-template-columns: 1fr; }

  .phrase__english-preview { display: none; }

  .flashcard__actions { gap: 8px; }
  .btn { padding: 10px 14px; }
}

@media (max-width: 420px) {
  .letter-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}