:root {
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-soft: #eef3f7;
  --text: #1f2933;
  --muted: #667085;
  --line: #d7dde5;
  --blue: #2563eb;
  --blue-dark: #1d4ed8;
  --green: #15803d;
  --green-soft: #dcfce7;
  --amber: #b7791f;
  --amber-soft: #fff7d6;
  --red: #b42318;
  --red-soft: #fee4e2;
  --shadow: 0 18px 48px rgba(31, 41, 51, 0.12);
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    linear-gradient(90deg, rgba(37, 99, 235, 0.05) 1px, transparent 1px),
    linear-gradient(rgba(21, 128, 61, 0.05) 1px, transparent 1px),
    var(--bg);
  background-size: 48px 48px;
  color: var(--text);
  font-family: Inter, "Segoe UI", Arial, sans-serif;
  line-height: 1.5;
}

button,
input,
textarea {
  font: inherit;
}

button {
  border: 0;
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.52;
}

input,
textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  padding: 12px 14px;
  outline: none;
}

input:focus,
textarea:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.16);
}

label {
  display: block;
  margin: 14px 0 6px;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
}

h1,
h2,
h3,
h4,
p {
  margin-top: 0;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 20px clamp(18px, 4vw, 48px);
  background: #17324d;
  color: #ffffff;
}

.topbar h1 {
  margin-bottom: 0;
  font-size: clamp(1.45rem, 3vw, 2rem);
  letter-spacing: 0;
}

.topbar .eyebrow {
  color: #b8d7ff;
}

.topbar-actions,
.button-row,
.lesson-header,
.panel-header,
.question-meta,
.dictionary-search {
  display: flex;
  align-items: center;
  gap: 10px;
}

.topbar-actions {
  justify-content: flex-end;
  flex-wrap: wrap;
}

.student-chip,
.score-pill,
.topic-badge,
.unit-badge {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 0.86rem;
  font-weight: 800;
  white-space: nowrap;
}

.student-chip {
  background: rgba(255, 255, 255, 0.14);
  color: #ffffff;
}

.score-pill {
  background: var(--green-soft);
  color: var(--green);
}

.topic-badge,
.unit-badge {
  background: #e8eefc;
  color: var(--blue-dark);
}

.app-shell {
  width: min(1240px, calc(100% - 32px));
  margin: 28px auto 48px;
}

.page {
  width: 100%;
}

.auth-layout,
.finish-layout {
  display: grid;
  min-height: calc(100vh - 190px);
  place-items: center;
}

.login-panel,
.finish-panel,
.lesson-main,
.teacher-panel,
.lesson-card {
  background: var(--surface);
  border: 1px solid rgba(215, 221, 229, 0.9);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.login-panel {
  width: min(430px, 100%);
  padding: 30px;
}

.finish-panel {
  width: min(520px, 100%);
  padding: 34px;
  text-align: center;
}

.finish-score {
  margin-bottom: 6px;
  color: var(--green);
  font-size: 2.3rem;
  font-weight: 900;
}

.dashboard-layout {
  display: grid;
  gap: 18px;
}

.section-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 16px;
}

.section-head h2,
.lesson-header h2,
.panel-header h2,
.finish-panel h2 {
  margin-bottom: 4px;
}

.eyebrow {
  margin-bottom: 4px;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.muted,
.status-text {
  color: var(--muted);
}

.status-text {
  min-height: 24px;
  margin-bottom: 0;
}

.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 16px;
}

.lesson-card {
  display: grid;
  align-content: start;
  gap: 12px;
  padding: 20px;
}

.lesson-card h3 {
  margin-bottom: 0;
  color: var(--text);
  font-size: 1.2rem;
}

.lesson-card p {
  color: var(--muted);
}

.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(340px, 0.7fr);
  gap: 18px;
  align-items: start;
}

.lesson-main,
.teacher-panel {
  padding: 22px;
}

.lesson-header,
.panel-header,
.question-meta {
  justify-content: space-between;
}

.progress-track {
  height: 10px;
  margin: 14px 0 20px;
  overflow: hidden;
  border-radius: 999px;
  background: #dfe7ef;
}

.progress-bar {
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--green), var(--blue));
  transition: width 0.25s ease;
}

.question-panel {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-soft);
}

.question-meta {
  margin-bottom: 14px;
  color: var(--muted);
  font-size: 0.92rem;
}

.question-text {
  margin-bottom: 18px;
  color: var(--text);
  font-size: clamp(1.25rem, 3vw, 1.9rem);
  font-weight: 800;
}

.exercise-area {
  display: grid;
  gap: 12px;
}

.answer-input {
  min-height: 54px;
  font-size: 1.2rem;
  font-weight: 700;
}

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

.choice-button {
  min-height: 52px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  font-size: 1.25rem;
  font-weight: 900;
}

.choice-button:hover,
.choice-button.selected {
  border-color: var(--blue);
  background: #e8eefc;
  color: var(--blue-dark);
}

.button-row {
  flex-wrap: wrap;
  margin-top: 16px;
}

.button-row.compact {
  margin-top: 8px;
}

.button-row.centered {
  justify-content: center;
}

.primary-button,
.secondary-button,
.ghost-button {
  min-height: 42px;
  border-radius: 8px;
  padding: 10px 16px;
  cursor: pointer;
  font-weight: 800;
}

.primary-button {
  background: var(--blue);
  color: #ffffff;
}

.primary-button:hover {
  background: var(--blue-dark);
}

.secondary-button {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
}

.secondary-button:hover {
  border-color: var(--blue);
  color: var(--blue-dark);
}

.ghost-button {
  border: 1px solid rgba(255, 255, 255, 0.28);
  background: rgba(255, 255, 255, 0.1);
  color: #ffffff;
}

.teacher-panel {
  display: grid;
  gap: 14px;
  position: sticky;
  top: 18px;
}

.teacher-panel .ghost-button {
  border-color: var(--line);
  background: var(--surface);
  color: var(--text);
}

.chat-box {
  display: flex;
  flex-direction: column;
  gap: 10px;
  height: 330px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f9fafb;
  padding: 12px;
}

.chat-message {
  width: min(92%, 520px);
  border-radius: 8px;
  padding: 10px 12px;
}

.chat-message.teacher {
  align-self: flex-start;
  border-left: 4px solid var(--blue);
  background: #eaf1ff;
}

.chat-message.student {
  align-self: flex-end;
  border-left: 4px solid var(--green);
  background: var(--green-soft);
}

.message-label {
  display: block;
  margin-bottom: 4px;
  font-size: 0.78rem;
  font-weight: 900;
  text-transform: uppercase;
  color: var(--muted);
}

.chat-message p {
  margin-bottom: 0;
  white-space: pre-line;
}

.chat-controls textarea {
  resize: vertical;
  min-height: 92px;
}

.toggle-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.toggle-row input {
  width: auto;
}

.dictionary-panel {
  display: grid;
  gap: 10px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.dictionary-panel h3 {
  margin-bottom: 0;
  font-size: 1rem;
}

.compact-header {
  align-items: flex-start;
}

.dictionary-search {
  align-items: stretch;
}

.dictionary-search input {
  min-width: 0;
}

.dictionary-result {
  min-height: 62px;
  border-radius: 8px;
  background: var(--amber-soft);
  color: #53390a;
  padding: 12px;
}

.dictionary-result h4 {
  margin-bottom: 4px;
}

.dictionary-result p {
  margin-bottom: 6px;
}

.example-text {
  color: var(--muted);
  font-style: italic;
}

.hint-box,
.result {
  margin-top: 12px;
  border-radius: 8px;
  padding: 12px;
}

.hint-box {
  border-left: 4px solid var(--amber);
  background: var(--amber-soft);
  color: #53390a;
}

.result {
  margin-bottom: 0;
  font-weight: 800;
}

.result.success {
  background: var(--green-soft);
  color: var(--green);
}

.result.warning {
  background: var(--red-soft);
  color: var(--red);
}

.result.neutral {
  background: #edf2f7;
  color: var(--text);
}

.loading {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: grid;
  place-items: center;
  background: rgba(255, 255, 255, 0.72);
}

.loader {
  width: 58px;
  height: 58px;
  border: 6px solid #d7dde5;
  border-top-color: var(--blue);
  border-radius: 999px;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

body.dark {
  --bg: #101828;
  --surface: #172033;
  --surface-soft: #121a2b;
  --text: #f5f7fa;
  --muted: #a8b3c7;
  --line: #344054;
  --shadow: 0 18px 48px rgba(0, 0, 0, 0.28);
}

body.dark .topbar {
  background: #0b1220;
}

body.dark .chat-box {
  background: #111827;
}

body.dark .chat-message.teacher {
  background: #182b4e;
}

body.dark .chat-message.student {
  background: #123522;
}

body.dark .topic-badge,
body.dark .unit-badge {
  background: #1b3261;
  color: #c7d7ff;
}

body.dark .score-pill {
  background: #123522;
  color: #95e7b1;
}

body.dark .dictionary-result,
body.dark .hint-box {
  background: #3d2f12;
  color: #ffe7ad;
}

body.dark .loading {
  background: rgba(16, 24, 40, 0.72);
}

@media (max-width: 960px) {
  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .teacher-panel {
    position: static;
  }
}

@media (max-width: 680px) {
  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .app-shell {
    width: min(100% - 20px, 1240px);
    margin-top: 16px;
  }

  .login-panel,
  .finish-panel,
  .lesson-main,
  .teacher-panel {
    padding: 16px;
  }

  .lesson-header,
  .panel-header,
  .question-meta,
  .dictionary-search {
    align-items: stretch;
    flex-direction: column;
  }

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

  .button-row.centered {
    display: flex;
  }

  .primary-button,
  .secondary-button,
  .ghost-button {
    width: 100%;
  }

  .chat-box {
    height: 300px;
  }
}