:root {
  color-scheme: light;
  --ink: #14211f;
  --muted: #5c6c70;
  --line: #d7e2e1;
  --paper: #f4f7f7;
  --panel: #ffffff;
  --accent: #286f6c;
  --accent-strong: #1d5552;
  --accent-soft: #dff1ef;
  --blue: #315f95;
  --blue-soft: #e6eef8;
  --gold: #946316;
  --gold-soft: #fff0d4;
  --rose: #a13d55;
  --rose-soft: #fde8ee;
  --ok: #237a4a;
  --bad: #b33a31;
  --shadow: 0 18px 45px rgba(31, 47, 70, 0.10);
  --radius: 8px;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

html,
body {
  overflow-x: hidden;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    linear-gradient(180deg, rgba(40, 111, 108, 0.07), rgba(244, 247, 247, 0) 260px),
    var(--paper);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

a,
button,
input,
textarea,
summary {
  touch-action: manipulation;
}

button,
input,
textarea {
  font: inherit;
}

button {
  cursor: pointer;
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible {
  outline: 3px solid rgba(40, 111, 108, 0.28);
  outline-offset: 2px;
}

.app-shell {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  display: flex;
  flex-direction: column;
  gap: 22px;
  height: 100vh;
  padding: 24px;
  background: #ffffff;
  border-right: 1px solid var(--line);
  overflow-y: auto;
}

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

.brand-mark {
  display: block;
  flex: 0 0 46px;
  width: 46px;
  height: 46px;
  object-fit: cover;
  border-radius: 14px;
  box-shadow: 0 10px 26px rgba(23, 63, 61, 0.18);
}

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

h1 {
  font-size: 1.03rem;
  line-height: 1.2;
}

h2 {
  font-size: clamp(1.65rem, 3vw, 2.5rem);
  line-height: 1.05;
}

h3 {
  font-size: 1.1rem;
}

.main p,
.main li,
.main summary,
.main label,
.main strong,
.main span {
  overflow-wrap: anywhere;
}

.eyebrow {
  color: var(--accent-strong);
  font-size: 0.74rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.muted {
  color: var(--muted);
}

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

.nav-item,
.ghost-button,
.primary-button,
.secondary-button,
.icon-button {
  border: 1px solid transparent;
  border-radius: var(--radius);
}

.nav-item {
  width: 100%;
  min-height: 44px;
  padding: 11px 12px;
  color: var(--ink);
  background: transparent;
  text-align: left;
}

.nav-item:hover,
.nav-item.active {
  background: var(--accent-soft);
  color: var(--accent-strong);
}

.progress-panel,
.card,
.exercise-card,
.tutor-panel,
.summary-card,
.topic-list,
.exam-console {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.progress-panel {
  display: grid;
  gap: 12px;
  padding: 16px;
  box-shadow: none;
}

.panel-row,
.split-row,
.metric-row {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
}

.progress-track {
  height: 9px;
  overflow: hidden;
  border-radius: 999px;
  background: #e8eef4;
}

.progress-fill {
  width: 0%;
  height: 100%;
  background: var(--accent);
  transition: width 180ms ease;
}

.ghost-button,
.secondary-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 12px;
  background: #ffffff;
  border-color: var(--line);
  color: var(--ink);
  text-decoration: none;
}

.ghost-button:hover,
.secondary-button:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.primary-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 11px 14px;
  color: #ffffff;
  background: var(--accent);
  text-decoration: none;
}

.primary-button:hover {
  background: var(--accent-strong);
}

.primary-button:disabled,
.secondary-button:disabled,
.ghost-button:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.main {
  min-width: 0;
  padding: 28px;
  padding-bottom: 42px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  align-items: flex-start;
  margin-bottom: 24px;
}

.exam-chip {
  display: grid;
  gap: 3px;
  min-width: 190px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.exam-chip span {
  color: var(--muted);
  font-size: 0.78rem;
}

.view {
  display: grid;
  gap: 18px;
}

.grid {
  display: grid;
  gap: 16px;
}

.grid.two {
  grid-template-columns: minmax(0, 1.1fr) minmax(280px, 0.9fr);
}

.grid.three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.card,
.tutor-panel,
.summary-card,
.topic-list,
.exam-console {
  min-width: 0;
  padding: 20px;
}

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

.video-card {
  display: grid;
  gap: 14px;
  min-width: 0;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.video-card p {
  color: var(--muted);
  line-height: 1.45;
}

.hero {
  display: grid;
  gap: 18px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background:
    linear-gradient(120deg, rgba(40, 111, 108, 0.13), rgba(47, 95, 159, 0.10)),
    #ffffff;
}

.hero p {
  max-width: 76ch;
  color: var(--muted);
  line-height: 1.55;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.stat {
  display: grid;
  gap: 6px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.stat strong {
  font-size: 1.7rem;
}

.pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.pill {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 5px 9px;
  border: 0;
  border-radius: 999px;
  background: var(--blue-soft);
  color: var(--blue);
  font-size: 0.82rem;
  font-weight: 700;
}

.pill.warn {
  background: var(--gold-soft);
  color: var(--gold);
}

.pill.good {
  background: #e1f3e9;
  color: var(--ok);
}

.pill.bad {
  background: var(--rose-soft);
  color: var(--rose);
}

.diagnostic-form {
  display: grid;
  gap: 16px;
}

.question {
  display: grid;
  gap: 10px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.choice {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fbfcfe;
}

.choice input {
  margin-top: 3px;
}

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

.topic-item {
  display: grid;
  gap: 9px;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.topic-item.locked {
  opacity: 0.62;
}

.topic-item-header {
  display: flex;
  justify-content: space-between;
  gap: 12px;
}

.topic-item button {
  justify-self: start;
}

.tutor-panel {
  display: grid;
  gap: 16px;
}

.teacher-line {
  display: grid;
  gap: 8px;
  padding: 16px;
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  border-radius: var(--radius);
}

.lesson-step {
  display: grid;
  gap: 10px;
  line-height: 1.55;
}

.lesson-step ul,
.summary-card ul,
.solution-list {
  margin: 0;
  padding-left: 1.2rem;
}

.lesson-step li,
.summary-card li,
.solution-list li {
  margin: 6px 0;
}

.example-box,
.feedback-box,
.hint-box,
.checkpoint-box,
.coach-note,
.deep-dive {
  display: grid;
  gap: 8px;
  padding: 14px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: #fbfcfe;
}

.coach-note {
  border-color: rgba(159, 107, 25, 0.28);
  background: var(--gold-soft);
}

.deep-dive {
  gap: 14px;
  background: #ffffff;
}

.deep-section {
  display: grid;
  gap: 8px;
}

.deep-section ul {
  margin: 0;
  padding-left: 1.2rem;
}

.deep-section li {
  margin: 6px 0;
  line-height: 1.5;
}

.coverage-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 12px;
}

.coverage-item {
  display: grid;
  gap: 8px;
  min-width: 0;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fbfcfe;
}

.coverage-item p {
  margin: 0;
  overflow-wrap: anywhere;
  color: var(--muted);
  line-height: 1.45;
}

.mini-options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 9px;
}

.mini-option {
  min-height: 44px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink);
  background: #ffffff;
  text-align: left;
}

.mini-option:hover,
.mini-option:focus-visible {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent-strong);
}

.mini-option:disabled {
  cursor: not-allowed;
  opacity: 0.62;
  background: #f3f6f8;
}

.reinforcement-panel {
  display: grid;
  gap: 12px;
}

.feedback-box.correct {
  border-color: rgba(35, 122, 74, 0.35);
  background: #eef8f2;
}

.feedback-box.incorrect {
  border-color: rgba(179, 58, 49, 0.35);
  background: #fff0ef;
}

.exercise-card {
  display: grid;
  gap: 14px;
  padding: 18px;
  box-shadow: none;
}

.answer-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.text-answer {
  width: min(420px, 100%);
  min-height: 46px;
  padding: 11px 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  font-size: 1rem;
}

.difficulty-tabs,
.topic-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tab-button {
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.tab-button.active {
  color: #ffffff;
  background: var(--accent);
  border-color: var(--accent);
}

.summary-card {
  display: grid;
  gap: 12px;
}

.summary-card p {
  line-height: 1.55;
}

.exam-console {
  display: grid;
  gap: 16px;
}

.timer {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  align-items: center;
  padding: 14px;
  border-radius: var(--radius);
  background: var(--blue-soft);
  color: var(--blue);
}

.timer strong {
  font-size: 1.45rem;
}

.exam-item {
  display: grid;
  gap: 10px;
  min-width: 0;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.exam-item p,
.lesson-step p,
.summary-card p,
.teacher-line p,
.feedback-box p,
.hint-box p,
.coach-note p {
  overflow-wrap: anywhere;
}

.source-list {
  display: grid;
  gap: 8px;
}

.source-list a {
  color: var(--blue);
}

.official-exams {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.official-exams summary {
  min-height: 36px;
  cursor: pointer;
  font-weight: 800;
}

.official-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 12px;
}

.official-link {
  display: grid;
  gap: 5px;
  min-width: 0;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink);
  text-decoration: none;
  background: #fbfcfe;
}

.official-link:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.official-link span {
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.35;
}

.manual-score-label {
  display: grid;
  gap: 7px;
  color: var(--muted);
  font-weight: 700;
}

.auth-form {
  display: grid;
  gap: 14px;
}

.auth-form label {
  display: grid;
  gap: 7px;
  color: var(--muted);
  font-weight: 700;
}

.form-error {
  min-height: 1.2em;
  color: var(--bad);
}

.form-error.success {
  color: var(--ok);
}

.empty-state {
  padding: 24px;
  border: 1px dashed var(--line);
  border-radius: var(--radius);
  background: #ffffff;
  color: var(--muted);
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: sticky;
    z-index: 20;
    top: 0;
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    height: auto;
    padding: 14px 16px;
  }

  .brand {
    align-items: center;
  }

  .brand-mark {
    width: 40px;
    height: 40px;
    flex-basis: 40px;
  }

  .nav {
    display: flex;
    gap: 8px;
    overflow-x: auto;
    padding-bottom: 4px;
    scrollbar-width: thin;
  }

  .nav-item {
    flex: 0 0 auto;
    width: auto;
    min-width: 104px;
    text-align: center;
    white-space: nowrap;
  }

  .progress-panel {
    display: none;
  }

  #resetProgress,
  #logoutStudent {
    display: none;
  }

  .grid.two,
  .grid.three,
  .video-grid {
    grid-template-columns: 1fr;
  }

  .topbar {
    flex-direction: column;
  }

  .main {
    padding: 18px;
    padding-bottom: 98px;
  }
}

@media (max-width: 640px) {
  h1 {
    font-size: 0.98rem;
  }

  h2 {
    font-size: 1.55rem;
    line-height: 1.12;
  }

  h3 {
    font-size: 1rem;
  }

  .main,
  .sidebar {
    padding: 14px;
  }

  .sidebar {
    gap: 10px;
  }

  .nav {
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 40;
    display: grid;
    grid-template-columns: repeat(6, minmax(0, 1fr));
    gap: 0;
    padding: 8px 8px calc(8px + env(safe-area-inset-bottom));
    border-top: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.96);
    box-shadow: 0 -12px 30px rgba(31, 47, 70, 0.10);
    overflow: visible;
  }

  .nav-item {
    min-width: 0;
    min-height: 48px;
    padding: 8px 4px;
    font-size: 0.72rem;
    text-align: center;
  }

  .brand {
    gap: 10px;
  }

  .brand-mark {
    width: 36px;
    height: 36px;
    flex-basis: 36px;
    font-size: 0.82rem;
  }

  .topbar {
    margin-bottom: 16px;
  }

  .exam-chip {
    width: 100%;
    min-width: 0;
  }

  .hero,
  .card,
  .tutor-panel,
  .summary-card,
  .topic-list,
  .exam-console {
    padding: 16px;
  }

  .actions {
    display: grid;
    grid-template-columns: 1fr;
    width: 100%;
  }

  .actions > button,
  .actions > a {
    width: 100%;
  }

  .difficulty-tabs,
  .topic-tabs,
  .pill-row {
    display: flex;
    overflow-x: auto;
    flex-wrap: nowrap;
    padding-bottom: 4px;
  }

  .tab-button,
  .pill {
    flex: 0 0 auto;
  }

  .topic-item-header,
  .split-row,
  .timer {
    align-items: flex-start;
    flex-direction: column;
  }

  .mini-options {
    grid-template-columns: 1fr;
  }

  .choice {
    min-height: 48px;
  }

  .timer {
    gap: 8px;
  }

  .timer strong {
    font-size: 1.25rem;
  }

  .auth-form .text-answer,
  .answer-row .text-answer,
  .exam-answer {
    width: 100%;
  }

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