/* Font shared with the RianKeng design system (see assets/riankeng.css) */
@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Sans+Thai:wght@400;500;600;700&display=swap');

/* Color tokens aligned to the RianKeng design system palette */
:root {
  --green: #1c7c50;       /* rk-green-700 */
  --green-dark: #123f2b;  /* rk-green-900 */
  --green-mid: #17613f;   /* rk-green-800 */
  --green-soft: #e7f3ec;  /* rk-green-100 */
  --paper: #fffdf4;
  --ink: #0d2c22;
  --muted: #52665d;
  --line: #c9ded0;
  --yellow: #f5d84c;
  --yellow-dark: #b59606;
  --blue: #3b82c4;
  --red: #c9483d;
  --radius: 8px;
  --rk-font: "IBM Plex Sans Thai", system-ui, -apple-system, "Segoe UI", sans-serif;

  /* Variable colors — each slider/variable gets one */
  --v0: #2563eb;   /* blue   */
  --v1: #d97706;   /* amber  */
  --v2: #7c3aed;   /* violet */
  --v3: #0891b2;   /* cyan   */
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--rk-font);
  background: #eef2ef;
  line-height: 1.65;
  letter-spacing: 0;
}

button,
input {
  font: inherit;
}

a {
  color: inherit;
}

.shell {
  width: min(1160px, calc(100% - 24px));
  margin: 0 auto;
  padding: 24px 0 42px;
}

.hero {
  color: #fff;
  background: var(--green);
  margin: -24px 0 0;
  padding: 24px 0;
}

.hero-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.mark {
  display: grid;
  width: 54px;
  height: 54px;
  flex: 0 0 auto;
  place-items: center;
  border: 3px solid rgba(255, 255, 255, 0.9);
  border-radius: 8px;
  background: var(--yellow);
  color: var(--green-dark);
  font-size: 1.45rem;
  font-weight: 950;
  box-shadow: 0 8px 22px rgba(3, 33, 19, 0.22);
}

h1,
h2,
h3,
p {
  margin: 0;
}

h1 {
  font-size: clamp(2.05rem, 6vw, 4.75rem);
  line-height: 1;
  letter-spacing: 0;
}

h2 {
  font-size: clamp(1.55rem, 4vw, 2.65rem);
  line-height: 1.1;
  letter-spacing: 0;
}

.platform {
  margin-bottom: 4px;
  font-weight: 900;
  opacity: 0.94;
}

.subtitle {
  margin-top: 8px;
  font-size: clamp(1rem, 3vw, 1.35rem);
  font-weight: 850;
}

.badge {
  flex: 0 0 auto;
  max-width: 230px;
  padding: 12px 14px;
  border: 2px solid rgba(255, 255, 255, 0.78);
  border-radius: var(--radius);
  background: var(--yellow);
  color: #10261a;
  text-align: center;
  font-weight: 950;
  box-shadow: 0 5px 0 var(--yellow-dark);
}

.topic-update {
  display: grid;
  gap: 4px;
  margin-top: 18px;
  padding: 14px 16px;
  border: 2px solid rgba(255, 255, 255, 0.72);
  border-radius: var(--radius);
  background: var(--paper);
  color: var(--ink);
  box-shadow: 0 6px 0 rgba(3, 33, 19, 0.18);
}

.topic-update span {
  color: var(--green);
  font-size: 0.88rem;
  font-weight: 950;
}

.topic-update strong {
  color: var(--green-dark);
  font-size: clamp(1.2rem, 3vw, 2rem);
  line-height: 1.15;
}

.topic-update p {
  color: var(--muted);
  font-size: clamp(0.98rem, 2vw, 1.12rem);
  font-weight: 750;
}

.site-nav {
  margin-top: 14px;
}

.menu-toggle {
  display: none;
  width: 100%;
  min-height: 48px;
  border: 0;
  border-radius: var(--radius);
  background: var(--paper);
  color: var(--green-dark);
  font-weight: 900;
  box-shadow: 0 5px 0 rgba(3, 33, 19, 0.22);
  cursor: pointer;
}

.menu-links {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.menu-links a {
  display: inline-flex;
  min-height: 42px;
  align-items: center;
  padding: 8px 12px;
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: var(--radius);
  background: rgba(15, 59, 41, 0.58);
  color: #fff;
  text-decoration: none;
  font-weight: 850;
}

main {
  display: grid;
  gap: 14px;
  margin-top: 18px;
}

.card {
  padding: clamp(18px, 4vw, 28px);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.97);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.11);
}

.step {
  display: block;
  margin-bottom: 6px;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 900;
}

.lead {
  margin-top: 12px;
  max-width: 860px;
  font-size: clamp(1.05rem, 2vw, 1.22rem);
}

.pill-row,
.formula-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.pill,
.formula-chip {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 6px 10px;
  border-radius: 8px;
  background: var(--green-soft);
  color: var(--green-dark);
  font-weight: 850;
}

.audio-grid {
  display: grid;
  grid-template-columns: 1.3fr 1fr;
  gap: 10px;
  margin-top: 14px;
}

.button {
  min-height: 52px;
  border: 2px solid var(--green-dark);
  border-radius: var(--radius);
  background: var(--yellow);
  color: var(--ink);
  font-weight: 950;
  cursor: pointer;
  box-shadow: 0 5px 0 var(--yellow-dark);
}

.button:disabled {
  opacity: 0.58;
  cursor: not-allowed;
  box-shadow: none;
}

.button.secondary {
  background: var(--green-soft);
  box-shadow: 0 5px 0 #b8d1c1;
}

.speed-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

.speed-button {
  min-height: 44px;
  border: 1px solid var(--green-dark);
  border-radius: var(--radius);
  background: var(--green-soft);
  color: var(--ink);
  font-weight: 900;
  cursor: pointer;
  box-shadow: 0 4px 0 #b8d1c1;
}

.speed-button.active {
  background: var(--yellow);
  box-shadow: 0 4px 0 var(--yellow-dark);
}

.audio-status {
  grid-column: 1 / -1;
  color: var(--muted);
  font-weight: 750;
}

.lesson-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(300px, 0.8fr);
  gap: 14px;
  align-items: start;
}

.simulation-card {
  display: grid;
  gap: 14px;
}

#controls-top {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

#controls-top:empty {
  display: none;
}

#controls-top .control {
  flex: 1 1 140px;
  padding: 8px 10px;
}

#controls-top .control-label {
  font-size: 0.88rem;
}

#controls-top .control input {
  margin-top: 6px;
}

.canvas-wrap {
  border: 3px solid var(--green-dark);
  border-radius: var(--radius);
  background: #f9fff9;
  overflow: hidden;
}

canvas {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.metric {
  min-height: 86px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #f7fbf8;
}

.metric span {
  display: block;
  color: var(--muted);
  font-weight: 750;
}

.metric strong {
  display: block;
  margin-top: 4px;
  color: var(--green-dark);
  font-size: clamp(1.35rem, 3vw, 1.9rem);
  line-height: 1;
}

.controls {
  position: sticky;
  top: 10px;
  display: grid;
  gap: 10px;
}

.controls.card {
  padding: clamp(14px, 2.2vw, 20px);
}

.controls h2 {
  font-size: clamp(1.35rem, 2vw, 1.9rem);
  line-height: 1.15;
}

.control {
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #f7fbf8;
}

.control-label {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px;
  color: var(--green-dark);
  font-size: 1.05rem;
  font-weight: 950;
  line-height: 1.2;
  overflow-wrap: anywhere;
  min-width: 0;
}

.controls .control-label {
  align-items: center;
  flex-wrap: wrap;
  font-size: clamp(0.95rem, 1.15vw, 1.05rem);
}

.controls .control-label strong {
  margin-left: auto;
}

.control input {
  width: 100%;
  margin-top: 10px;
  accent-color: var(--green);
}

.formula-panel {
  display: grid;
  gap: 10px;
}

.formula-line {
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  font-size: clamp(0.95rem, 2.4vw, 1.08rem);
  font-weight: 850;
  overflow-wrap: anywhere;
}

.controls .formula-line {
  padding: 10px;
  font-size: clamp(0.92rem, 1.15vw, 1rem);
  line-height: 1.45;
}

.value {
  display: inline-block;
  margin: 2px;
  padding: 2px 8px;
  border-radius: 7px;
  background: #daf3e7;
  color: #07543a;
  font-weight: 950;
}

/* ── Variable color chips v0–v3 ──────────────────────────── */
.value.v0 { background: #dbeafe; color: var(--v0); }
.value.v1 { background: #fef3c7; color: var(--v1); }
.value.v2 { background: #ede9fe; color: var(--v2); }
.value.v3 { background: #cffafe; color: var(--v3); }

/* ── Slider dot + colored value label ────────────────────── */
.ctrl-dot {
  display: inline-block;
  width: 9px; height: 9px;
  border-radius: 50%;
  flex-shrink: 0;
  margin-right: 5px;
  vertical-align: middle;
  margin-bottom: 1px;
}

.ctrl-val-0 { color: var(--v0); }
.ctrl-val-1 { color: var(--v1); }
.ctrl-val-2 { color: var(--v2); }
.ctrl-val-3 { color: var(--v3); }

/* ── Multi-select chip control (checkbox-style toggle group) ─ */
.control-chip-multi { padding: 12px; border: 1px solid var(--line); border-radius: var(--radius); background: #f7fbf8; }
.chip-row { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.chip-toggle {
  padding: 8px 14px;
  border-radius: 999px;
  border: 2px solid var(--line);
  background: #fff;
  color: var(--green-dark);
  font-weight: 850;
  font-size: 0.95rem;
  cursor: pointer;
  transition: all 0.15s ease;
}
.chip-toggle:hover { border-color: var(--green); }
.chip-toggle--active {
  background: var(--green);
  border-color: var(--green);
  color: #fff;
}

/* ── Per-variable slider accent ──────────────────────────── */
.ctrl-v0 input { accent-color: var(--v0); }
.ctrl-v1 input { accent-color: var(--v1); }
.ctrl-v2 input { accent-color: var(--v2); }
.ctrl-v3 input { accent-color: var(--v3); }

.note {
  color: var(--muted);
  font-size: 0.95rem;
}

.vocab-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
  gap: 10px;
  margin-top: 14px;
}

.vocab-card {
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  display: grid;
  gap: 1px;
}

.vocab-word {
  font-size: 1.05rem;
  font-weight: 900;
  color: var(--green-dark);
}

.vocab-arrow {
  font-size: 0.75rem;
  color: var(--muted);
  font-weight: 700;
  margin-top: 4px;
}

.vocab-read {
  font-size: 1rem;
  font-weight: 850;
  color: var(--green);
  letter-spacing: 0.03em;
}

.vocab-meaning {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 4px;
  line-height: 1.4;
}

/* ── Weakness analysis panel (วิเคราะห์จุดอ่อน) ── */
.weakness-panel {
  display: grid;
  gap: 6px;
  margin: 12px 0 4px;
}

.weakness-panel:empty {
  display: none;
}

.weak-head {
  font-size: 0.9rem;
  color: var(--green-dark);
  padding: 4px 0;
}

.weak-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-left-width: 5px;
  border-radius: var(--radius);
  background: #fff;
}

.weak-name {
  font-weight: 800;
  color: var(--green-dark);
  font-size: 0.9rem;
}

.weak-score {
  font-size: 0.82rem;
  font-weight: 800;
  white-space: nowrap;
}

.weak-weak {
  border-left-color: #e24b4a;
  background: #fcebeb;
}
.weak-weak .weak-score { color: #a32d2d; }

.weak-strong {
  border-left-color: var(--green);
  background: var(--green-soft);
}
.weak-strong .weak-score { color: var(--green); }

.weak-untried {
  border-left-color: var(--line);
}
.weak-untried .weak-score { color: var(--muted); }

.weak-tip {
  font-size: 0.84rem;
  color: var(--green-dark);
  background: var(--yellow);
  padding: 10px 12px;
  border-radius: var(--radius);
  line-height: 1.45;
  margin-top: 4px;
}

.quiz-list {
  display: grid;
  gap: 12px;
  margin-top: 14px;
}

/* ── Collapsible quiz groups ── */
.quiz-group {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}

.quiz-group-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 14px;
  background: #f4faf6;
  cursor: pointer;
  list-style: none;
  user-select: none;
  font-weight: 700;
}
.quiz-group-header::-webkit-details-marker { display: none; }
.quiz-group-header::before {
  content: "▶";
  font-size: 0.7rem;
  color: var(--green);
  transition: transform 0.2s;
}
details[open] > .quiz-group-header::before { transform: rotate(90deg); }

.quiz-group-title { font-size: 1rem; color: var(--ink); }
.quiz-group-sub   { font-size: 0.8rem; color: var(--muted); font-weight: 600; }
.quiz-group-badge {
  margin-left: auto;
  background: var(--green);
  color: #fff;
  font-size: 0.75rem;
  font-weight: 800;
  padding: 2px 8px;
  border-radius: 99px;
}

.quiz-group-inner {
  display: grid;
  gap: 10px;
  padding: 12px;
  background: #fff;
}

/* ── Timer start button ── */
.timer-start-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 10px;
  padding: 7px 16px;
  border: 1.5px solid var(--green);
  border-radius: 99px;
  background: #fff;
  color: var(--green-dark);
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
}
.timer-start-btn:disabled {
  border-color: var(--line);
  color: var(--muted);
  cursor: default;
}

/* ── Floating timer chip ── */
.quiz-timer-chip {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 999;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 16px;
  background: #1a3a2a;
  color: #fff;
  border-radius: 99px;
  box-shadow: 0 4px 16px rgba(0,0,0,0.25);
  font-weight: 800;
  font-size: 1.1rem;
  transition: opacity 0.3s;
}
.quiz-timer-chip.hidden { display: none; }
.quiz-timer-chip.done   { background: var(--green); }

.timer-stop-btn {
  padding: 3px 12px;
  border: 1.5px solid rgba(255,255,255,0.5);
  border-radius: 99px;
  background: transparent;
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  cursor: pointer;
}

.question {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fbfffc;
}

.question h3 {
  font-size: 1.05rem;
}

.choices {
  display: grid;
  gap: 8px;
  margin-top: 10px;
}

.choice {
  min-height: 44px;
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  text-align: left;
  cursor: pointer;
}

.choice.correct {
  border-color: var(--green);
  background: #def6e9;
  font-weight: 900;
}

.choice.wrong {
  border-color: var(--red);
  background: #fff0ee;
}

.feedback {
  margin-top: 8px;
  color: var(--green-dark);
  font-weight: 780;
}

/* ── Vocab highlights — marker-pen feel ─────────────────── */
.rk-hl {
  background: linear-gradient(
    104deg,
    transparent 0.9%,
    rgba(245, 216, 76, 0) 2.4%,
    rgba(245, 216, 76, 0.52) 4%,
    rgba(245, 216, 76, 0.52) 90%,
    rgba(245, 216, 76, 0.1) 93%,
    transparent 95%
  );
  border-radius: 3px 1px 4px 2px / 2px 4px 1px 3px;
  padding: 0 3px;
  margin: 0 -1px;
  cursor: help;
  font-weight: inherit;
  color: inherit;
  position: relative;
  transition: background 0.2s;
}

.rk-hl:hover,
.rk-hl.hl-active {
  background: linear-gradient(
    104deg,
    transparent 0.9%,
    rgba(245, 216, 76, 0) 2.4%,
    rgba(245, 216, 76, 0.82) 4%,
    rgba(245, 216, 76, 0.82) 90%,
    rgba(245, 216, 76, 0.2) 93%,
    transparent 95%
  );
}

/* ── Sticky-note tooltip ─────────────────────────────────── */
#rk-tooltip {
  position: fixed;
  z-index: 9999;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.15s;
  max-width: 270px;
  min-width: 160px;
}

#rk-tooltip.visible {
  opacity: 1;
}

.rk-tip-inner {
  background: #fffde6;
  border: 1px solid #e0c840;
  border-left: 4px solid var(--yellow-dark);
  border-radius: 2px 6px 6px 2px;
  padding: 10px 14px 12px;
  box-shadow: 3px 4px 12px rgba(0,0,0,0.18);
  transform: rotate(-1.3deg);
  /* lined-paper lines */
  background-image: repeating-linear-gradient(
    to bottom,
    transparent,
    transparent 21px,
    rgba(100,160,255,0.13) 21px,
    rgba(100,160,255,0.13) 22px
  );
  line-height: 22px;
}

.rk-tip-word {
  display: block;
  font-size: 1.05rem;
  font-weight: 900;
  color: var(--ink);
  margin-bottom: 2px;
}

.rk-tip-read {
  display: block;
  font-size: 0.78rem;
  color: var(--green);
  font-weight: 600;
  margin-bottom: 6px;
}

.rk-tip-read::before { content: "อ่านว่า "; color: var(--muted); font-weight: 400; }

.rk-tip-meaning {
  display: block;
  font-size: 0.88rem;
  color: var(--ink);
  font-weight: 500;
  line-height: 1.5;
}

/* ── Worked example (Option A) ─────────────────────────── */
.example-card {
  background: #f6fef9;
  border: 2px solid var(--green);
  border-radius: var(--radius);
  padding: 18px 20px;
}

.example-tag {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--green);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin: 0 0 6px;
}

.example-prompt {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 0 0 16px;
}

/* ── Solution panel (shared A + B) ─────────────────────── */
.solution-panel {
  display: grid;
  gap: 14px;
}

.solution-explanation {
  background: #fffde7;
  border-left: 4px solid var(--yellow-dark);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 12px 14px;
}

.solution-label {
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--yellow-dark);
  margin: 0 0 4px;
}

.solution-graph {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #eef2ef;
  padding: 8px;
  display: flex;
  justify-content: center;
}

.solution-graph canvas {
  max-width: 100%;
  height: auto;
}

.solution-explanation p:last-child {
  margin: 0;
  font-weight: 600;
  line-height: 1.6;
}

.solution-choices {
  display: grid;
  gap: 8px;
}

.solution-choice {
  border-radius: var(--radius);
  border: 1.5px solid var(--line);
  padding: 10px 12px;
  display: grid;
  grid-template-columns: 28px 1fr;
  gap: 6px 10px;
  align-items: start;
}

.sc-correct {
  border-color: var(--green);
  background: #e8faf0;
}

.sc-wrong {
  border-color: var(--line);
  background: #fff8f8;
}

.sc-badge {
  font-size: 1.1rem;
  font-weight: 900;
  line-height: 1.5;
}

.sc-correct .sc-badge { color: var(--green); }
.sc-wrong  .sc-badge { color: var(--red); }

.sc-text {
  font-weight: 600;
  line-height: 1.5;
  grid-column: 2;
}

.sc-correct .sc-text { color: var(--green-dark); }

.sc-why {
  grid-column: 2;
  margin: 2px 0 0;
  font-size: 0.88rem;
  color: var(--muted);
  line-height: 1.5;
}

/* ── "ดูเฉลย" button (Option B) ────────────────────────── */
.show-solution-btn {
  margin-top: 10px;
  padding: 6px 16px;
  border: 1.5px solid var(--green);
  border-radius: 20px;
  background: transparent;
  color: var(--green);
  font-size: 0.88rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.show-solution-btn:hover {
  background: var(--green);
  color: #fff;
}

.solution-panel-wrap {
  margin-top: 12px;
  border-top: 1px solid var(--line);
  padding-top: 12px;
}

.solution-panel-wrap.hidden {
  display: none;
}

.footer {
  margin-top: 18px;
  color: var(--muted);
  text-align: center;
}

@media (max-width: 860px) {
  .hero-row,
  .lesson-grid,
  .audio-grid,
  .result-grid {
    grid-template-columns: 1fr;
  }

  .hero-row {
    align-items: flex-start;
  }

  .badge {
    max-width: none;
  }

  .controls {
    position: static;
    order: -1;
  }

  .lesson-grid {
    display: flex;
    flex-direction: column;
  }
}

@media (max-width: 620px) {
  .shell {
    width: min(100% - 16px, 1160px);
    padding-top: 14px;
  }

  .hero {
    margin-top: -14px;
  }

  .menu-toggle {
    display: block;
  }

  .menu-links {
    display: none;
    margin-top: 8px;
  }

  .hero-row {
    flex-direction: column;
    align-items: stretch;
  }

  .brand {
    width: 100%;
  }

  .site-nav.open .menu-links {
    display: grid;
  }

  .menu-links a,
  .button,
  .speed-button {
    width: 100%;
    justify-content: center;
  }

  .speed-row {
    grid-template-columns: 1fr;
  }

  .card {
    padding: 16px;
  }

  canvas {
    aspect-ratio: 4 / 3;
  }
}

/* ── PDF Download Button (screen) ──────────────────────────── */
.pdf-download-btn {
  background: var(--green);
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 8px 16px;
  font: 600 13px/1 var(--rk-font);
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
}
.pdf-download-btn:hover { opacity: 0.85; }

/* ── PDF Sheet (screen: hidden) ────────────────────────────── */
#pdf-sheet { display: none; }

/* ── Print styles ──────────────────────────────────────────── */
@media print {
  @page { size: A4 portrait; margin: 14mm 14mm 18mm 14mm; }

  /* Hide everything except the PDF sheet */
  body > *:not(#pdf-sheet),
  #rk-lesson { display: none !important; }

  #pdf-sheet {
    display: block !important;
    font-family: "IBM Plex Sans Thai", system-ui, sans-serif;
    font-size: 10.5pt;
    color: #111;
    line-height: 1.55;
  }

  /* ── Header ── */
  .pdf-header {
    border-bottom: 2pt solid #1c7c50;
    padding-bottom: 10pt;
    margin-bottom: 12pt;
  }
  .pdf-brand-row {
    display: flex;
    align-items: flex-start;
    gap: 10pt;
  }
  .pdf-mark {
    background: #1c7c50;
    color: #fff;
    font-size: 16pt;
    font-weight: 700;
    width: 40pt;
    height: 40pt;
    border-radius: 7pt;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
  }
  .pdf-titles { flex: 1; }
  .pdf-brand-name { font-size: 7.5pt; color: #666; margin: 0 0 2pt; }
  .pdf-title { font-size: 17pt; font-weight: 700; color: #0a2e1c; margin: 0 0 2pt; }
  .pdf-subtitle { font-size: 9pt; color: #555; margin: 0; }

  .pdf-qr-block { text-align: center; flex-shrink: 0; margin-left: auto; }
  .pdf-qr-label { font-size: 7.5pt; color: #444; margin: 3pt 0 0; }

  /* ── Sections ── */
  .pdf-section {
    margin: 11pt 0;
    page-break-inside: avoid;
  }
  .pdf-sh {
    font-size: 11.5pt;
    font-weight: 700;
    color: #1c7c50;
    border-left: 3pt solid #1c7c50;
    padding-left: 7pt;
    margin: 0 0 6pt;
    page-break-after: avoid;
  }

  /* ── Vocab table ── */
  .pdf-vocab { width: 100%; border-collapse: collapse; font-size: 9.5pt; }
  .pdf-vocab td { padding: 3pt 6pt; border-bottom: 0.5pt solid #ddd; vertical-align: top; }
  .pdf-vocab td:first-child { width: 22%; }
  .pdf-vocab td:nth-child(2) { width: 22%; color: #555; }

  /* ── Quiz ── */
  .pdf-quiz-grid {
    column-count: 2;
    column-gap: 16pt;
  }
  .pdf-question {
    break-inside: avoid;
    margin-bottom: 8pt;
  }
  .pdf-qp { font-size: 9.5pt; margin: 0 0 3pt; }
  .pdf-choices {
    margin-left: 10pt;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1pt 8pt;
  }
  .pdf-choice { font-size: 9pt; display: flex; gap: 4pt; align-items: baseline; }
  .pdf-clabel { font-weight: 700; color: #1c7c50; min-width: 12pt; }

  /* ── Footer ── */
  .pdf-foot {
    margin-top: 14pt;
    padding-top: 6pt;
    border-top: 0.5pt solid #ccc;
    font-size: 7.5pt;
    color: #888;
  }
}