:root {
  color-scheme: light;
  --ink: #162029;
  --muted: #637181;
  --line: #dbe3ea;
  --paper: #fbfcf8;
  --panel: #ffffff;
  --blue: #1b6ca8;
  --blue-2: #dceffc;
  --green: #1d7b56;
  --green-2: #dff5eb;
  --red: #b43a3a;
  --red-2: #ffe6e2;
  --lavender: #8f79e8;
  --lavender-2: #f0ecff;
  --rose: #ff8bb8;
  --yellow: #f5b642;
  --shadow: 0 18px 50px rgba(34, 49, 63, 0.13);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 12% 8%, rgba(143, 121, 232, 0.15), transparent 28%),
    radial-gradient(circle at 88% 14%, rgba(255, 139, 184, 0.12), transparent 24%),
    linear-gradient(135deg, #f7fbff 0%, #fbfcf8 48%, #f6f2ff 100%);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  display: grid;
  grid-template-columns: 292px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  display: flex;
  flex-direction: column;
  gap: 18px;
  height: 100vh;
  padding: 22px;
  border-right: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.78);
  backdrop-filter: blur(18px);
}

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

.brand-mark {
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--ink), var(--lavender));
  color: #fff;
  font-weight: 900;
}

.brand p,
.brand h1 {
  margin: 0;
}

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

.brand h1 {
  font-size: 1.35rem;
  letter-spacing: 0;
}

.progress-card,
.focus-box,
.topic-panel,
.lesson-panel,
.quiz-start,
.quiz-run,
.results,
.data-tools,
.overall-progress,
.progress-topic {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.88);
  box-shadow: var(--shadow);
}

.progress-card,
.focus-box {
  padding: 16px;
  box-shadow: none;
}

.mascot-box {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  margin-top: auto;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.7);
}

.mini-heart {
  display: inline-grid;
  place-items: center;
  width: 28px;
  height: 28px;
  color: var(--heart-color);
  font-size: 28px;
  line-height: 1;
  filter: drop-shadow(0 5px 8px rgba(22, 32, 41, 0.12));
}

.mini-heart::before {
  content: "♥";
}

.mini-heart.rose {
  --heart-color: #ff7ba9;
}

.mini-heart.lavender {
  --heart-color: #a796ff;
}

.mini-heart.blue {
  --heart-color: #91d8ff;
}

.mini-heart.yellow {
  --heart-color: #ffe58a;
}

.spark {
  position: relative;
  width: 22px;
  height: 22px;
}

.spark::before,
.spark::after {
  position: absolute;
  content: "";
  inset: 9px 2px;
  border-radius: 999px;
  background: var(--lavender);
}

.spark::after {
  transform: rotate(90deg);
}

.progress-card > div:first-child {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}

.progress-card strong {
  font-size: 2rem;
}

.mini-track,
.quiz-track {
  overflow: hidden;
  height: 10px;
  border-radius: 999px;
  background: #e8edf1;
}

.mini-track span,
.quiz-track span {
  display: block;
  width: 0%;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--green), var(--blue));
  transition: width 240ms ease;
}

.progress-card p,
.focus-box p,
.section-title p {
  color: var(--muted);
}

.nav-tabs {
  display: grid;
  gap: 8px;
}

.nav-tab,
.ghost-button,
.secondary-button,
.primary-button,
.answer-button,
.topic-button {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  transition: transform 160ms ease, border-color 160ms ease, background 160ms ease;
}

.nav-tab,
.ghost-button,
.secondary-button,
.primary-button {
  min-height: 44px;
  padding: 10px 14px;
  font-weight: 800;
}

.nav-tab {
  text-align: left;
}

.nav-tab.active,
.topic-button.active {
  border-color: rgba(143, 121, 232, 0.42);
  background: var(--lavender-2);
}

.primary-button {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.secondary-button {
  border-color: rgba(29, 123, 86, 0.35);
  background: var(--green-2);
  color: #0f5a3c;
}

.sound-button[aria-pressed="true"] {
  border-color: rgba(180, 58, 58, 0.35);
  background: var(--red-2);
  color: #7e2525;
}

.brand h1::after,
.section-title h3::after {
  content: "  *";
  color: var(--lavender);
}

button:hover:not(:disabled) {
  transform: translateY(-1px);
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

main {
  min-width: 0;
  padding: 24px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 18px;
}

.top-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 10px;
}

.topbar h2,
.section-title h3 {
  margin: 4px 0 0;
  letter-spacing: 0;
}

.section-title {
  position: relative;
}

.quiz-start .section-title,
.results,
.lesson-panel {
  position: relative;
  overflow: hidden;
}

.feedback {
  position: relative;
  overflow: hidden;
  padding-right: 14px;
}

.topbar h2 {
  font-size: clamp(1.7rem, 3vw, 3rem);
}

.eyebrow {
  color: var(--lavender);
  font-size: 0.72rem;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

.study-layout {
  display: grid;
  grid-template-columns: minmax(250px, 350px) minmax(0, 1fr);
  gap: 18px;
}

.topic-panel,
.lesson-panel,
.quiz-start,
.quiz-run,
.results {
  padding: 20px;
}

.topic-list {
  display: grid;
  gap: 10px;
  margin-top: 16px;
}

.topic-button {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  width: 100%;
  min-height: 56px;
  padding: 12px;
  text-align: left;
}

.topic-button span {
  color: var(--muted);
  font-size: 0.8rem;
}

.lesson-hero {
  display: grid;
  gap: 14px;
}

.lesson-hero h3 {
  margin: 0;
  font-size: clamp(1.5rem, 3vw, 2.4rem);
}

.key-grid,
.config-grid,
.progress-grid,
.stat-grid {
  display: grid;
  gap: 12px;
}

.key-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 18px 0;
}

.key-card,
.stat-card {
  min-width: 0;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f8fbfd;
}

.key-card strong,
.stat-card strong {
  display: block;
  margin-bottom: 6px;
}

.key-card p,
.stat-card p {
  margin: 0;
  color: var(--muted);
}

.detail-list {
  margin: 16px 0;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.detail-list strong {
  display: block;
  margin-bottom: 10px;
}

.detail-list ul {
  display: grid;
  gap: 8px;
  margin: 0;
  padding-left: 20px;
  color: var(--muted);
}

.formula-box {
  margin: 14px 0;
  padding: 16px;
  border-left: 5px solid var(--yellow);
  border-radius: 8px;
  background: #fff8e6;
  font-weight: 850;
}

.curve {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  align-items: end;
  gap: 8px;
  min-height: 170px;
  margin-top: 16px;
  padding: 14px;
  border: 1px dashed #b8c5cf;
  border-radius: 8px;
  background: linear-gradient(#fff, #f7fafc);
}

.curve-step {
  display: grid;
  align-content: end;
  min-height: var(--h);
  padding: 8px;
  border-radius: 8px;
  background: var(--blue-2);
  color: #124c78;
  font-size: 0.82rem;
  font-weight: 800;
}

.config-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 22px 0;
}

label {
  display: grid;
  gap: 8px;
  color: var(--muted);
  font-weight: 800;
}

select {
  width: 100%;
  min-height: 46px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
}

.quiz-actions,
.quiz-footer,
.data-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.hidden {
  display: none !important;
}

.quiz-header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
}

.quiz-header h3 {
  margin: 4px 0 12px;
  font-size: clamp(1.25rem, 2.4vw, 2rem);
}

.score-pill {
  flex: 0 0 auto;
  padding: 10px 12px;
  border-radius: 999px;
  background: var(--green-2);
  color: #0f5a3c;
  font-weight: 900;
}

.answers {
  display: grid;
  gap: 10px;
  margin: 18px 0;
}

.answer-button {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  align-items: center;
  gap: 12px;
  width: 100%;
  min-height: 58px;
  padding: 11px 13px;
  text-align: left;
}

.answer-letter {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: #eef3f6;
  font-weight: 900;
}

.answer-button.correct {
  border-color: rgba(29, 123, 86, 0.45);
  background: var(--green-2);
}

.answer-button.wrong {
  border-color: rgba(180, 58, 58, 0.45);
  background: var(--red-2);
}

.feedback {
  margin-bottom: 14px;
  padding: 14px;
  border-radius: 8px;
  background: #eef6ff;
  border: 1px solid #cfe3f5;
}

.feedback strong {
  display: block;
  margin-bottom: 6px;
}

.feedback.good {
  background: var(--green-2);
  border-color: rgba(29, 123, 86, 0.25);
}

.feedback.bad {
  background: var(--red-2);
  border-color: rgba(180, 58, 58, 0.25);
}

.results h3 {
  margin-top: 0;
  font-size: clamp(1.5rem, 3vw, 2.4rem);
}

.stat-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 16px 0;
}

.progress-grid {
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.overall-progress {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 14px;
  align-items: center;
  margin: 16px 0;
  padding: 18px;
}

.overall-progress strong {
  display: block;
  font-size: clamp(2rem, 5vw, 3.4rem);
}

.overall-progress p {
  margin: 6px 0 0;
  color: var(--muted);
}

.overall-progress .mini-heart {
  width: 72px;
  height: 72px;
  font-size: 72px;
}

.data-tools {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin: 16px 0;
  padding: 16px;
}

.data-tools p {
  margin: 6px 0 0;
  color: var(--muted);
}

.import-button {
  display: inline-grid;
  place-items: center;
  min-height: 44px;
  padding: 10px 14px;
  border: 1px solid rgba(29, 123, 86, 0.35);
  border-radius: 8px;
  background: var(--green-2);
  color: #0f5a3c;
  font-weight: 800;
  cursor: pointer;
}

.data-actions input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.progress-topic {
  padding: 16px;
}

.progress-topic h4 {
  margin: 0 0 8px;
}

.progress-topic p {
  margin: 8px 0 0;
  color: var(--muted);
}

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

.tag {
  padding: 7px 10px;
  border-radius: 999px;
  background: #edf2f5;
  color: #40505f;
  font-size: 0.84rem;
  font-weight: 800;
}

.unit-chip {
  display: inline-block;
  margin-right: 8px;
  padding: 4px 8px;
  border-radius: 999px;
  background: var(--lavender-2);
  color: #654dc7;
  font-size: 0.72rem;
  font-weight: 900;
  vertical-align: middle;
}

@media (max-width: 920px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .nav-tabs {
    grid-template-columns: repeat(3, 1fr);
  }

  .nav-tab {
    text-align: center;
  }

  .study-layout,
  .config-grid,
  .stat-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 560px) {
  main,
  .sidebar {
    padding: 14px;
  }

  .topbar,
  .quiz-header,
  .data-tools {
    align-items: stretch;
    flex-direction: column;
  }

  .top-actions {
    justify-content: stretch;
  }

  .top-actions > button {
    flex: 1 1 150px;
  }

  .key-grid {
    grid-template-columns: 1fr;
  }

  .curve {
    grid-template-columns: 1fr;
    min-height: auto;
  }

  .curve-step {
    min-height: 54px;
  }

  .answer-button {
    grid-template-columns: 30px minmax(0, 1fr);
  }

  .feedback {
    padding-right: 14px;
  }
}