:root {
  color-scheme: light;
  --bg: #f7f8f5;
  --surface: #ffffff;
  --surface-soft: #eef4f7;
  --ink: #1d2528;
  --muted: #647076;
  --line: #d9e0de;
  --green: #2f7d50;
  --green-soft: #e5f2e9;
  --green-line: #9ccdab;
  --blue: #256aa8;
  --blue-soft: #e4f0fa;
  --blue-line: #9fc6e5;
  --amber: #f1b53a;
  --amber-soft: #fff4d8;
  --red: #b33b32;
  --red-soft: #fae6e3;
  --red-line: #e0a09a;
  --radius: 8px;
  --shadow: 0 14px 36px rgba(22, 36, 39, 0.08);
  --font: "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 18px;
  line-height: 1.55;
}

button,
input,
select,
textarea {
  font: inherit;
}

button,
a.button {
  min-height: 44px;
}

a {
  color: inherit;
}

img {
  display: block;
  max-width: 100%;
}

.wrap {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(247, 248, 245, 0.96);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(12px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 76px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  width: 42px;
  height: 42px;
  place-items: center;
  border-radius: var(--radius);
  background: var(--ink);
  color: #fff;
  font-weight: 800;
}

.brand strong,
.brand small {
  display: block;
}

.brand strong {
  font-size: 1rem;
}

.brand small {
  color: var(--muted);
  font-size: 0.82rem;
}

.quick-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
}

.quick-nav a,
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  font-size: 0.9rem;
  font-weight: 700;
  text-decoration: none;
}

.quick-nav a.active {
  border-color: currentColor;
}

main.wrap {
  padding: 34px 0 64px;
}

.loading-card,
.error-card,
.intro,
.module-hero,
.section-panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.loading-card,
.error-card {
  padding: 28px;
}

.intro {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 24px;
  align-items: stretch;
  padding: 28px;
}

.intro h1,
.module-hero h1 {
  margin: 0;
  max-width: 900px;
  font-size: clamp(2rem, 5vw, 4.4rem);
  line-height: 1.05;
  letter-spacing: 0;
}

.intro p,
.module-hero p {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 1.08rem;
}

.intro-steps {
  display: grid;
  align-content: start;
  gap: 10px;
  padding: 18px;
  background: var(--surface-soft);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.step-row {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 10px;
  align-items: center;
}

.step-row span {
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  border-radius: 50%;
  background: var(--surface);
  color: var(--ink);
  font-weight: 800;
}

.module-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-top: 22px;
}

.module-card {
  position: relative;
  display: grid;
  gap: 12px;
  min-height: 240px;
  padding: 22px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
  text-align: left;
  text-decoration: none;
}

.module-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 7px;
  background: var(--module-color);
}

.module-card h2 {
  margin: 0;
  font-size: clamp(1.55rem, 3vw, 2.25rem);
  line-height: 1.12;
  letter-spacing: 0;
}

.module-card p {
  margin: 0;
  color: var(--muted);
}

.module-card .card-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: auto;
}

.subject-chip,
.status-chip,
.required-chip {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  min-height: 32px;
  padding: 5px 10px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 800;
  line-height: 1.2;
}

.subject-chip {
  background: var(--module-soft);
  color: var(--module-color);
}

.status-chip {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--muted);
}

.status-chip.done {
  border-color: var(--green-line);
  background: var(--green-soft);
  color: var(--green);
}

.required-chip {
  background: var(--amber-soft);
  color: #725100;
}

.module-theme-bio {
  --module-color: var(--green);
  --module-soft: var(--green-soft);
  --module-line: var(--green-line);
}

.module-theme-physics {
  --module-color: var(--blue);
  --module-soft: var(--blue-soft);
  --module-line: var(--blue-line);
}

.module-hero {
  padding: 28px;
  border-top: 7px solid var(--module-color);
}

.hero-topline,
.section-title-row,
.activity-title-row,
.quiz-title-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.module-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  gap: 18px;
  align-items: start;
  margin-top: 18px;
}

.module-main {
  display: grid;
  gap: 18px;
}

.module-side {
  position: sticky;
  top: 94px;
  display: grid;
  gap: 14px;
}

.section-panel {
  padding: 24px;
}

.section-panel h2,
.section-panel h3 {
  margin: 0;
  line-height: 1.16;
  letter-spacing: 0;
}

.section-panel h2 {
  font-size: 1.65rem;
}

.section-panel h3 {
  font-size: 1.25rem;
}

.section-panel > p,
.activity-card > p {
  margin: 10px 0 0;
  color: var(--muted);
}

.task-list,
.notes-list,
.checklist-list {
  margin: 16px 0 0;
  padding: 0;
  list-style: none;
}

.task-list li,
.notes-list li {
  position: relative;
  padding: 10px 0 10px 34px;
  border-bottom: 1px solid var(--line);
}

.task-list li::before,
.notes-list li::before {
  content: "";
  position: absolute;
  top: 18px;
  left: 8px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--module-color);
}

.task-list li:last-child,
.notes-list li:last-child {
  border-bottom: 0;
}

.actions,
.inline-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

.button,
button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 15px;
  border: 1px solid transparent;
  border-radius: var(--radius);
  background: var(--ink);
  color: #fff;
  font-weight: 800;
  line-height: 1.25;
  text-decoration: none;
  cursor: pointer;
}

.button.primary {
  background: var(--module-color);
}

.button.secondary,
button.secondary {
  border-color: var(--line);
  background: var(--surface);
  color: var(--ink);
}

.button.ghost,
button.ghost {
  border-color: transparent;
  background: transparent;
  color: var(--ink);
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.62;
}

button:focus-visible,
a:focus-visible,
select:focus-visible,
textarea:focus-visible,
input:focus-visible {
  outline: 3px solid var(--amber);
  outline-offset: 3px;
}

.explanation-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.fact-card {
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.fact-card strong {
  display: block;
  margin-bottom: 6px;
  color: var(--module-color);
  font-size: 0.9rem;
  text-transform: uppercase;
}

.notes-box {
  margin-top: 16px;
  border: 2px solid var(--module-line);
  border-radius: var(--radius);
  background: var(--module-soft);
}

.notes-list {
  margin: 0;
  padding: 6px 18px;
}

.activity-list {
  display: grid;
  gap: 16px;
  margin-top: 16px;
}

.activity-card,
.quiz-question {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.activity-card {
  padding: 18px;
}

.recognition-stage {
  display: grid;
  grid-template-columns: minmax(240px, 0.95fr) minmax(260px, 1fr);
  gap: 16px;
  align-items: stretch;
  margin-top: 16px;
}

.plant-visual {
  display: grid;
  min-height: 280px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.plant-visual img {
  width: 100%;
  height: 100%;
  min-height: 280px;
  object-fit: cover;
}

.image-placeholder {
  display: grid;
  min-height: 280px;
  place-items: center;
  padding: 24px;
  color: var(--muted);
  text-align: center;
}

.hint-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
}

.hint-list li {
  padding: 5px 9px;
  border-radius: 999px;
  background: var(--amber-soft);
  color: #725100;
  font-size: 0.86rem;
  font-weight: 700;
}

.choice-grid,
.answer-grid {
  display: grid;
  gap: 10px;
  margin-top: 14px;
}

.choice-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.choice-grid button,
.answer-grid button {
  justify-content: flex-start;
  min-height: 50px;
  border-color: var(--line);
  background: var(--surface);
  color: var(--ink);
  text-align: left;
}

.choice-grid button.correct,
.answer-grid button.correct {
  border-color: var(--green);
  background: var(--green-soft);
  color: var(--green);
}

.choice-grid button.incorrect,
.answer-grid button.incorrect {
  border-color: var(--red);
  background: var(--red-soft);
  color: var(--red);
}

.feedback,
.quiz-result {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: var(--radius);
  background: var(--surface-soft);
  border: 1px solid var(--line);
  font-weight: 700;
}

.feedback.good,
.quiz-result.good {
  background: var(--green-soft);
  border-color: var(--green-line);
  color: var(--green);
}

.feedback.bad,
.quiz-result.bad {
  background: var(--red-soft);
  border-color: var(--red-line);
  color: var(--red);
}

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

.form-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(170px, 260px);
  gap: 12px;
  align-items: center;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.form-row select,
.form-row textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
}

.form-row select {
  min-height: 44px;
  padding: 8px 10px;
}

textarea {
  min-height: 120px;
  padding: 12px;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
}

.tf-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 12px;
  align-items: center;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.segmented {
  display: inline-grid;
  grid-template-columns: 1fr 1fr;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.segmented button {
  min-height: 42px;
  border: 0;
  border-radius: 0;
  background: transparent;
  color: var(--ink);
}

.segmented button.active {
  background: var(--module-color);
  color: #fff;
}

.model-box {
  display: none;
  margin-top: 12px;
  padding: 14px;
  border-left: 5px solid var(--module-color);
  border-radius: var(--radius);
  background: var(--module-soft);
}

.model-box.visible {
  display: block;
}

.gas-lab {
  margin-top: 16px;
}

.gas-chamber {
  position: relative;
  width: 100%;
  height: 260px;
  overflow: hidden;
  border: 2px solid var(--blue-line);
  border-radius: var(--radius);
  background: var(--blue-soft);
  transition: width 180ms ease;
}

.gas-lab.compressed .gas-chamber {
  width: 66%;
}

.particle {
  position: absolute;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--blue);
  opacity: 0.88;
  animation: drift 3s linear infinite alternate;
}

.gas-lab.compressed .particle {
  animation-duration: 1.55s;
}

.particle:nth-child(1) { left: 9%; top: 18%; animation-delay: -0.2s; }
.particle:nth-child(2) { left: 28%; top: 58%; animation-delay: -1.1s; }
.particle:nth-child(3) { left: 48%; top: 32%; animation-delay: -2.2s; }
.particle:nth-child(4) { left: 70%; top: 70%; animation-delay: -0.7s; }
.particle:nth-child(5) { left: 82%; top: 18%; animation-delay: -1.8s; }
.particle:nth-child(6) { left: 18%; top: 78%; animation-delay: -2.8s; }
.particle:nth-child(7) { left: 60%; top: 52%; animation-delay: -1.5s; }
.particle:nth-child(8) { left: 38%; top: 12%; animation-delay: -2.5s; }

@keyframes drift {
  from { transform: translate(0, 0); }
  to { transform: translate(28px, 22px); }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .particle {
    animation: none;
  }

  .gas-chamber {
    transition: none;
  }
}

.quiz-form {
  display: grid;
  gap: 14px;
  margin-top: 16px;
}

.quiz-question {
  padding: 16px;
}

.quiz-question fieldset {
  margin: 0;
  padding: 0;
  border: 0;
}

.quiz-question legend {
  margin-bottom: 12px;
  font-weight: 800;
}

.quiz-options {
  display: grid;
  gap: 10px;
}

.quiz-options label {
  display: grid;
  grid-template-columns: 24px 1fr;
  gap: 10px;
  align-items: start;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.quiz-options input {
  width: 20px;
  height: 20px;
  margin-top: 2px;
}

.option-feedback {
  display: none;
  margin-top: 10px;
  padding: 10px;
  border-radius: var(--radius);
}

.quiz-question.answered .option-feedback {
  display: block;
}

.quiz-question.correct-answer .option-feedback {
  background: var(--green-soft);
  color: var(--green);
}

.quiz-question.wrong-answer .option-feedback {
  background: var(--red-soft);
  color: var(--red);
}

.side-card {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}

.side-card h2,
.side-card h3 {
  margin: 0;
  font-size: 1.18rem;
  line-height: 1.2;
}

.checklist-list {
  display: grid;
  gap: 10px;
}

.checklist-list label {
  display: grid;
  grid-template-columns: 24px 1fr;
  gap: 10px;
  align-items: start;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.checklist-list input {
  width: 20px;
  height: 20px;
  margin-top: 2px;
  accent-color: var(--module-color);
}

.progress-meter {
  margin-top: 12px;
}

.meter-track {
  height: 12px;
  overflow: hidden;
  border-radius: 999px;
  background: var(--surface-soft);
}

.meter-fill {
  height: 100%;
  width: var(--meter, 0%);
  background: var(--module-color);
}

.meter-label {
  display: block;
  margin-top: 8px;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
}

.terms {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.terms span {
  padding: 5px 9px;
  border-radius: 999px;
  background: var(--surface-soft);
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 700;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 920px) {
  .header-inner,
  .intro,
  .module-layout,
  .recognition-stage {
    grid-template-columns: 1fr;
  }

  .header-inner {
    align-items: stretch;
  }

  .quick-nav {
    justify-content: flex-start;
    padding-bottom: 12px;
  }

  .module-side {
    position: static;
    grid-row: 1;
  }
}

@media (max-width: 720px) {
  body {
    font-size: 17px;
  }

  .wrap {
    width: min(100% - 22px, 1120px);
  }

  main.wrap {
    padding-top: 20px;
  }

  .intro,
  .module-hero,
  .section-panel,
  .activity-card {
    padding: 18px;
  }

  .module-grid,
  .explanation-grid,
  .choice-grid {
    grid-template-columns: 1fr;
  }

  .module-card {
    min-height: 200px;
  }

  .form-row,
  .tf-row {
    grid-template-columns: 1fr;
  }

  .segmented {
    width: 100%;
  }

  .gas-lab.compressed .gas-chamber {
    width: 78%;
  }
}