/* ==========================================================================
   Korean Flashcards
   Palette and sizing knobs live in :root, so most restyling happens there.
   ========================================================================== */

:root {
  --bg: #f7f4ef;
  --bg-tint: #efe9e0;
  --surface: #ffffff;
  --ink: #23201c;
  --ink-soft: #6c655c;
  --ink-faint: #a49b90;
  --accent: #c2563c;
  --accent-soft: #f3ded8;
  --line: #e4ddd3;

  --shadow-card: 0 1px 2px rgba(35, 32, 28, 0.06),
                 0 12px 24px -8px rgba(35, 32, 28, 0.18),
                 0 28px 56px -20px rgba(35, 32, 28, 0.22);
  --shadow-btn: 0 1px 2px rgba(35, 32, 28, 0.08);

  --radius-card: 24px;
  --radius-btn: 12px;
  --control-h: 44px;

  --flip-duration: 0.55s;
  --flip-ease: cubic-bezier(0.2, 0.8, 0.25, 1);

  /* Korean fallbacks first so Hangul never lands on a substituted glyph. */
  --font-stack: "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans KR",
                -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
                Helvetica, Arial, sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  min-height: 100vh;
  background:
    radial-gradient(1200px 600px at 50% -10%, var(--bg-tint), transparent 70%),
    var(--bg);
  color: var(--ink);
  font-family: var(--font-stack);
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
}

.app {
  min-height: 100vh;
  min-height: 100dvh; /* accounts for mobile browser chrome */
  max-width: 720px;
  margin: 0 auto;
  padding: clamp(16px, 4vw, 32px);
  display: flex;
  flex-direction: column;
  gap: clamp(16px, 3vw, 28px);
}

/* ---------- Header: deck picker + start-language toggle ---------- */

.app-header {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.app-title {
  margin: 0;
  font-size: clamp(1.25rem, 4.2vw, 1.65rem);
  font-weight: 400;
  letter-spacing: -0.02em;
  line-height: 1.15;
  text-align: center;
  color: var(--ink);
}

.app-nav {
  margin: 0;
  text-align: center;
  font-size: 0.88rem;
}

.app-nav a {
  color: var(--ink-muted, #6b6b68);
  text-decoration: none;
}

.app-nav a:hover {
  color: var(--ink);
  text-decoration: underline;
}

.app-nav-sep {
  margin: 0 0.35rem;
  color: var(--ink-faint, #aaa);
}

.settings {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  width: 100%;
}

.setting {
  display: flex;
  min-width: 0;
  width: 50%;
}

.deck-picker {
  width: 100%;
  height: 34px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background-color: var(--surface);
  box-shadow: var(--shadow-btn);
  appearance: none;
  -webkit-appearance: none;
  padding: 0 30px 0 12px;
  /* Chevron drawn inline so the app stays dependency-free. */
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1.5L6 6.5L11 1.5' stroke='%236c655c' stroke-width='1.75' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  color: var(--ink);
  font-family: inherit;
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.18s ease;
}

.deck-picker:hover {
  border-color: var(--ink-faint);
}

.day-filter {
  width: 100%;
  display: flex;
  justify-content: center;
}

.day-filter[hidden] {
  display: none;
}

.day-filter-group {
  display: inline-flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 3px;
  padding: 2px;
  border-radius: 8px;
  background-color: rgba(255, 255, 255, 0.5);
}

.day-filter-option {
  padding: 4px 9px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--ink-soft);
  font-family: inherit;
  font-size: 0.74rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease;
}

.day-filter-option:hover {
  color: var(--accent);
}

.day-filter-option.is-active {
  background-color: var(--accent-soft);
  color: var(--accent);
}

/* ---------- Stage: card + sentence ---------- */

.stage {
  flex: 1;
  min-height: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: clamp(16px, 3vw, 24px);
}

/* The card absorbs whatever height the rest of the UI does not need, so a
   two-line example sentence can never push the controls off a phone screen. */
.card-wrap {
  position: relative;
  perspective: 1400px;
  flex: 1 1 auto;
  min-height: 160px;
  max-height: 380px;
}

/* Pinned to the wrapper rather than sized with a percentage height, which
   would collapse to zero against a flex-sized parent. */
.card {
  position: absolute;
  inset: 0;
  cursor: pointer;
  outline: none;
  transition: transform 0.22s var(--flip-ease), opacity 0.22s ease;
}

.card:focus-visible .card-face {
  box-shadow: var(--shadow-card), 0 0 0 3px var(--accent-soft);
}

.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform var(--flip-duration) var(--flip-ease);
}

.card.is-flipped .card-inner {
  transform: rotateY(180deg);
}

.card-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: clamp(20px, 5vw, 36px);
  border: 1px solid var(--line);
  border-radius: var(--radius-card);
  background-color: var(--surface);
  box-shadow: var(--shadow-card);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  text-align: center;
  overflow: hidden;
}

.card-face--back {
  transform: rotateY(180deg);
  background:
    linear-gradient(170deg, #fffdfb 0%, var(--surface) 55%);
}

.card-hint {
  position: absolute;
  top: clamp(14px, 3vw, 20px);
  left: 0;
  right: 0;
  font-size: 0.68rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-faint);
}

.card-word {
  font-size: clamp(3.1rem, 14vw, 5.4rem);
  font-weight: 650;
  line-height: 1.16;
  letter-spacing: -0.015em;
  /* Long compounds like 머리카락 should shrink rather than clip. */
  max-width: 100%;
  overflow-wrap: break-word;
}

/* English words read better a touch smaller than Hangul at the same size,
   and some entries are short phrases that need room to wrap. */
.card-word[lang="en"] {
  font-size: clamp(2.3rem, 10.5vw, 4.4rem);
}

/* Length-aware steps, applied by sizeClass() in app.js. Phrase entries like
   '천천히 말해 주세요' or 'older brother (said by a male)' would otherwise
   overflow the card on a small screen. */
.card-word.is-sm {
  font-size: clamp(2rem, 8.5vw, 3.4rem);
}

.card-word.is-xs {
  font-size: clamp(1.6rem, 6.6vw, 2.7rem);
}

.card-word[lang="en"].is-sm {
  font-size: clamp(1.8rem, 7.5vw, 3rem);
}

.card-word[lang="en"].is-xs {
  font-size: clamp(1.4rem, 5.6vw, 2.3rem);
}

.card-romanization {
  font-size: clamp(1.2rem, 4.6vw, 1.6rem);
  font-weight: 500;
  font-style: italic;
  color: var(--ink-soft);
}

/* ---------- Discrete navigation arrows beside the card ---------- */

.card-nav {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  /* Above the card, which builds a 3D stacking context with preserve-3d. */
  z-index: 2;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background-color: transparent;
  color: var(--ink-faint);
  opacity: 0.45;
  cursor: pointer;
  transition: opacity 0.18s ease, background-color 0.18s ease, color 0.18s ease;
}

.card-nav svg {
  width: 22px;
  height: 22px;
}

.card-nav:hover,
.card-nav:focus-visible {
  opacity: 1;
  background-color: var(--accent-soft);
  color: var(--accent);
  outline: none;
}

.card-nav:active {
  transform: translateY(-50%) scale(0.92);
}

.card-nav--prev {
  left: 2px;
}

.card-nav--next {
  right: 2px;
}

/* Touch screens have no hover, so sit a little more visible at rest. */
@media (hover: none) {
  .card-nav {
    opacity: 0.55;
  }
}

/* Enough window to clear the 720px app: move the arrows off the card entirely. */
@media (min-width: 860px) {
  .card-nav--prev {
    left: -60px;
  }

  .card-nav--next {
    right: -60px;
  }
}

/* ---------- Speaker buttons ---------- */

.speak-btn {
  position: absolute;
  z-index: 3;
  pointer-events: auto;
  touch-action: manipulation;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background-color: transparent;
  color: var(--ink-faint);
  opacity: 0.45;
  cursor: pointer;
  transition: opacity 0.18s ease, background-color 0.18s ease, color 0.18s ease;
}

.speak-btn svg {
  width: 18px;
  height: 18px;
}

.speak-btn:hover,
.speak-btn:focus-visible {
  opacity: 1;
  background-color: var(--accent-soft);
  color: var(--accent);
  outline: none;
}

.speak-btn:active {
  transform: scale(0.92);
}

.speak-btn--card {
  right: clamp(10px, 2.5vw, 14px);
  bottom: clamp(10px, 2.5vw, 14px);
}

.speak-btn--sentence {
  right: clamp(10px, 2.5vw, 14px);
  bottom: clamp(10px, 2.5vw, 14px);
}

@media (hover: none) {
  .speak-btn {
    opacity: 0.55;
  }
}

/* Fade-and-slide when moving to another card, so the flip never plays in reverse. */
.card.is-changing {
  opacity: 0;
}

.card.is-changing--next {
  transform: translateX(14px);
}

.card.is-changing--prev {
  transform: translateX(-14px);
}

/* ---------- Sentence panel ---------- */

.sentence-panel {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: clamp(14px, 3vw, 18px) clamp(16px, 4vw, 22px);
  border: 1px solid var(--line);
  border-radius: 16px;
  background-color: rgba(255, 255, 255, 0.62);
  /* Title stays pinned at the top on both faces; min-height keeps the card
     from jumping when the breakdown appears on flip. */
  justify-content: flex-start;
  align-items: stretch;
  min-height: clamp(140px, 39vw, 210px);
  transition: opacity 0.2s ease;
}

/* Sentence and breakdown share one left-aligned block below the title. */
.sentence-content {
  display: flex;
  flex: 1;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 100%;
  text-align: center;
}

.sentence-panel.is-swapping {
  opacity: 0;
}

.sentence-label {
  flex-shrink: 0;
  font-size: 0.68rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-faint);
  text-align: left;
}

.sentence-text {
  margin: 0;
  width: 100%;
  font-size: clamp(1.5rem, 6vw, 2.4rem);
  font-weight: 500;
  line-height: 1.35;
  color: var(--ink);
  text-align: center;
}

/* Two-clause examples from the connectors deck run long. Stepping them down
   keeps the panel from swallowing the card on a phone. */
.sentence-text.is-sm {
  font-size: clamp(1.3rem, 5.2vw, 2rem);
}

.sentence-text.is-xs {
  font-size: clamp(1.15rem, 4.4vw, 1.7rem);
}

.sentence-text[lang="en"] {
  font-size: clamp(1.25rem, 5.2vw, 2rem);
}

.sentence-text[lang="en"].is-sm {
  font-size: clamp(1.1rem, 4.5vw, 1.75rem);
}

.sentence-text[lang="en"].is-xs {
  font-size: clamp(1rem, 3.9vw, 1.5rem);
}

.sentence-panel.is-answer .sentence-text[lang="en"] {
  font-size: clamp(1.15rem, 4.8vw, 1.875rem);
}

.sentence-panel.is-answer .sentence-text[lang="en"].is-sm {
  font-size: clamp(1.05rem, 4.2vw, 1.625rem);
}

.sentence-panel.is-answer .sentence-text[lang="en"].is-xs {
  font-size: clamp(0.95rem, 3.7vw, 1.4rem);
}

/* ---------- Word-by-word breakdown ---------- */

/* Each chunk is a little column: Korean on top, its meaning underneath, the
   way the sentences are annotated by hand. Wraps to another row when needed. */
.breakdown {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-start;
  align-items: flex-start;
  gap: 8px clamp(12px, 3vw, 18px);
  width: 100%;
  margin-top: 4px;
  padding-top: 10px;
  border-top: 1px solid var(--line);
}

.breakdown:empty {
  display: none;
}

.sentence-text[lang="en"] ~ .breakdown {
  justify-content: center;
}

.sentence-text[lang="en"] ~ .breakdown .chunk {
  align-items: center;
}

.sentence-text[lang="en"] ~ .breakdown .chunk-en {
  text-align: center;
}

.chunk {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 1px;
}

/* Answer side: English sentence and Korean chunks match; both a touch smaller
   than the Korean-only example on the front. */
.sentence-panel.is-answer .sentence-text {
  font-size: clamp(1.375rem, 5.75vw, 2.25rem);
}

.sentence-panel.is-answer .sentence-text.is-sm {
  font-size: clamp(1.2rem, 5vw, 1.875rem);
}

.sentence-panel.is-answer .sentence-text.is-xs {
  font-size: clamp(1.075rem, 4.2vw, 1.625rem);
}

.chunk-ko {
  font-size: clamp(1.375rem, 5.75vw, 2.25rem);
  font-weight: 600;
  line-height: 1.35;
  color: var(--ink);
  white-space: nowrap;
}

.sentence-panel.is-answer .sentence-text.is-sm ~ .breakdown .chunk-ko {
  font-size: clamp(1.2rem, 5vw, 1.875rem);
}

.sentence-panel.is-answer .sentence-text.is-xs ~ .breakdown .chunk-ko {
  font-size: clamp(1.075rem, 4.2vw, 1.625rem);
}

.chunk-particle {
  display: inline-block;
  margin-left: 1px;
  padding: 0 3px;
  border: 1px solid var(--accent);
  border-radius: 5px;
  color: var(--accent);
}

.chunk-en {
  font-size: clamp(0.875rem, 3.55vw, 1.075rem);
  font-weight: 500;
  line-height: 1.3;
  color: var(--ink-faint);
  text-align: left;
}

/* ---------- Footer: controls + progress ---------- */

.app-footer {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.controls {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  width: 100%;
}

.controls .btn {
  width: 100%;
  min-width: 0;
}

.btn {
  min-height: 46px;
  padding: 12px 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius-btn);
  background-color: var(--surface);
  box-shadow: var(--shadow-btn);
  color: var(--ink);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.12s ease, border-color 0.18s ease,
              background-color 0.18s ease, color 0.18s ease;
}

.btn:hover:not(:disabled) {
  border-color: var(--ink-faint);
}

.btn:active:not(:disabled) {
  transform: translateY(1px);
}

.btn:disabled {
  opacity: 0.4;
  cursor: default;
}

.btn--primary {
  border-color: var(--accent);
  background-color: var(--accent);
  color: #fff;
}

.btn--primary:hover:not(:disabled) {
  border-color: var(--accent);
  background-color: #ad4b34;
}

.progress {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: center;
}

.progress-text {
  margin: 0;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--ink-soft);
}

.progress-bar {
  width: 100%;
  height: 4px;
  border-radius: 99px;
  background-color: var(--line);
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  width: 0;
  border-radius: 99px;
  background-color: var(--accent);
  transition: width 0.3s var(--flip-ease);
}

.footer-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  min-height: 26px;
}

.lang-toggle {
  display: inline-flex;
  gap: 3px;
  padding: 2px;
  border-radius: 8px;
  background-color: rgba(255, 255, 255, 0.5);
  opacity: 0.55;
  transition: opacity 0.18s ease, background-color 0.18s ease;
}

.lang-toggle:hover,
.lang-toggle:focus-within {
  opacity: 0.85;
  background-color: var(--surface);
}

.lang-toggle-option {
  padding: 5px 10px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--ink-soft);
  font-family: inherit;
  font-size: 0.76rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease;
}

.lang-toggle-option:hover {
  color: var(--accent);
}

.lang-toggle-option.is-active {
  background-color: var(--accent-soft);
  color: var(--accent);
  opacity: 1;
}

.lang-toggle:hover .lang-toggle-option.is-active,
.lang-toggle:focus-within .lang-toggle-option.is-active {
  opacity: 1;
}

.shuffle-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background-color: transparent;
  color: var(--ink-faint);
  opacity: 0.35;
  cursor: pointer;
  touch-action: manipulation;
  transition: opacity 0.18s ease, background-color 0.18s ease, color 0.18s ease;
}

.shuffle-btn svg {
  width: 14px;
  height: 14px;
}

.shuffle-btn:hover,
.shuffle-btn:focus-visible {
  opacity: 0.7;
  background-color: var(--accent-soft);
  color: var(--accent);
  outline: none;
}

.shuffle-btn.is-active {
  opacity: 0.85;
  background-color: var(--accent-soft);
  color: var(--accent);
}

.shuffle-btn.is-active:hover,
.shuffle-btn.is-active:focus-visible {
  opacity: 1;
  background-color: var(--accent-soft);
  color: var(--accent);
}

.shuffle-btn:active {
  transform: scale(0.92);
}

.shuffle-btn:disabled {
  opacity: 0.2;
  cursor: default;
}

/* Very narrow screens: multi-word glosses such as "waist, lower back" need a
   step down in size to stay inside the card. */
@media (max-width: 360px) {
  .card-word {
    font-size: clamp(2.4rem, 12vw, 3.4rem);
  }

  .card-word[lang="en"] {
    font-size: clamp(1.8rem, 8vw, 2.6rem);
  }

  .card-word.is-sm {
    font-size: clamp(1.7rem, 7vw, 2.4rem);
  }

  .card-word.is-xs {
    font-size: clamp(1.35rem, 5.4vw, 1.9rem);
  }

  .card-word[lang="en"].is-sm {
    font-size: clamp(1.5rem, 6.2vw, 2.1rem);
  }

  .card-word[lang="en"].is-xs {
    font-size: clamp(1.15rem, 4.8vw, 1.6rem);
  }

  /* Breakdown chunks wrap to three rows at this width, so buy the rows back
     from the padding and the card floor rather than from the text size. */
  .card-wrap {
    min-height: 148px;
  }

  .sentence-panel {
    padding: 12px 14px;
  }

  .breakdown {
    gap: 6px 11px;
    padding-top: 8px;
  }
}

/* Short viewports: give the sentence and controls priority over card size. */
@media (max-height: 700px) {
  .app {
    gap: 12px;
  }

  .card-wrap {
    min-height: 125px;
  }

  .card-word {
    font-size: clamp(2.2rem, 9vw, 3.4rem);
  }

  .card-word[lang="en"] {
    font-size: clamp(1.7rem, 7vw, 2.6rem);
  }

  /* A 125px-tall card cannot hold a wrapped phrase at full size. */
  .card-word.is-sm {
    font-size: clamp(1.5rem, 6.2vw, 2.2rem);
  }

  .card-word.is-xs {
    font-size: clamp(1.2rem, 4.8vw, 1.7rem);
  }

  .card-word[lang="en"].is-sm {
    font-size: clamp(1.3rem, 5.4vw, 1.9rem);
  }

  .card-word[lang="en"].is-xs {
    font-size: clamp(1rem, 4.2vw, 1.4rem);
  }

  .card-romanization {
    font-size: clamp(0.95rem, 3.6vw, 1.2rem);
  }

  .sentence-panel {
    padding: 11px 13px;
    gap: 4px;
  }

  .sentence-text {
    font-size: clamp(1.25rem, 5vw, 1.8rem);
  }

  .sentence-panel.is-answer .sentence-text {
    font-size: clamp(1.125rem, 4.75vw, 1.675rem);
  }

  .sentence-text.is-sm {
    font-size: clamp(1.1rem, 4.4vw, 1.5rem);
  }

  .sentence-panel.is-answer .sentence-text.is-sm {
    font-size: clamp(1rem, 4.1vw, 1.4rem);
  }

  .sentence-text.is-xs {
    font-size: clamp(1rem, 3.8vw, 1.3rem);
  }

  .sentence-panel.is-answer .sentence-text.is-xs {
    font-size: clamp(0.925rem, 3.55vw, 1.2rem);
  }

  .chunk-ko {
    font-size: clamp(1.125rem, 4.75vw, 1.675rem);
  }

  .sentence-panel.is-answer .sentence-text.is-sm ~ .breakdown .chunk-ko {
    font-size: clamp(1rem, 4.1vw, 1.4rem);
  }

  .sentence-panel.is-answer .sentence-text.is-xs ~ .breakdown .chunk-ko {
    font-size: clamp(0.925rem, 3.55vw, 1.2rem);
  }

  .chunk-en {
    font-size: clamp(0.8rem, 3rem, 0.95rem);
  }

  .breakdown {
    padding-top: 6px;
    gap: 5px 10px;
    margin-top: 2px;
  }

}

@media (max-width: 520px) {
  .setting {
    width: 80%;
    max-width: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .card-inner,
  .card,
  .sentence-panel,
  .progress-bar-fill {
    transition-duration: 0.01ms;
  }
}