:root {
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-soft: #f0f3f8;
  --text: #172033;
  --muted: #64748b;
  --border: #d9e0ea;
  --primary: #1f4e79;
  --primary-dark: #173a5a;
  --success: #26734d;
  --danger: #9b1c1c;
  --warning-bg: #fff7e6;
  --warning-border: #f0cc7a;
  --code-bg: #111827;
  --code-text: #f9fafb;
  --inline-code-bg: #eef2f7;
  --shadow: 0 12px 30px rgba(23, 32, 51, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

header {
  background: linear-gradient(135deg, #173a5a, #245f92);
  color: white;
  padding: 42px 24px;
}

.home-page header {
  background: linear-gradient(135deg, #132f4c, #235f92);
  padding: 46px 24px 72px 24px;
}

.header-content {
  max-width: 1080px;
  margin: 0 auto;
}

.home-page .header-content,
.home-page main {
  max-width: 1100px;
}

header h1,
.home-page h1 {
  margin: 0 0 12px 0;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1.05;
  letter-spacing: -0.04em;
}

.home-page h1 {
  font-size: clamp(2.1rem, 5vw, 3.8rem);
  line-height: 1.02;
  letter-spacing: -0.05em;
}

header p {
  margin: 0;
  max-width: 850px;
  color: rgba(255, 255, 255, 0.88);
  font-size: 1.05rem;
}

.home-page header p {
  max-width: 760px;
  color: rgba(255, 255, 255, 0.86);
  font-size: 1.08rem;
}

main {
  max-width: 1080px;
  margin: -24px auto 0 auto;
  padding: 0 24px 48px 24px;
}

.home-page main {
  padding: 0 24px 56px 24px;
  margin-top: -42px;
}

.toolbar,
.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.toolbar {
  border-radius: 18px;
  padding: 18px;
  margin-bottom: 22px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 18px;
  align-items: center;
}

.panel {
  border-radius: 22px;
  padding: 22px;
  margin-bottom: 22px;
}

.progress-area {
  display: grid;
  gap: 8px;
}

.progress-text {
  font-weight: 700;
  font-size: 1rem;
}

.progress-bar {
  width: 100%;
  height: 10px;
  border-radius: 999px;
  background: var(--surface-soft);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  width: 0%;
  background: var(--success);
  border-radius: 999px;
  transition: width 0.2s ease;
}

.toolbar-actions,
.section-buttons {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.section-buttons {
  gap: 12px;
  justify-content: flex-start;
  margin-top: 18px;
}

button {
  cursor: pointer;
  border: 1px solid var(--primary);
  background: var(--primary);
  color: white;
  padding: 9px 13px;
  border-radius: 10px;
  font-weight: 650;
  font-size: 0.92rem;
}

.home-page button {
  border-radius: 12px;
  padding: 11px 15px;
  font-weight: 700;
  font-size: 0.95rem;
}

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

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

button.secondary:hover {
  background: var(--surface-soft);
}

button.answer-button {
  width: 100%;
  text-align: left;
  background: white;
  color: var(--text);
  border-color: var(--border);
  font-weight: 600;
}

button.answer-button:hover {
  background: var(--surface-soft);
  border-color: rgba(31, 78, 121, 0.5);
}

button.answer-button.correct {
  border-color: rgba(38, 115, 77, 0.55);
  background: #effaf3;
  color: var(--success);
}

button.answer-button.wrong {
  border-color: rgba(155, 28, 28, 0.45);
  background: #fff1f1;
  color: var(--danger);
}

button.answer-button:disabled {
  cursor: default;
}

.note,
.theory {
  background: var(--warning-bg);
  border: 1px solid var(--warning-border);
  border-radius: 16px;
  padding: 18px;
  margin-bottom: 22px;
}

.theory {
  background: var(--surface);
  border-color: var(--border);
  box-shadow: 0 6px 18px rgba(23, 32, 51, 0.04);
}

.note h2,
.theory h2,
.sidebar h2,
.content h2 {
  margin: 0 0 8px 0;
  font-size: 1.1rem;
}

.sidebar h2,
.content h2 {
  margin-bottom: 14px;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
}

.note ul,
.theory ul {
  margin-bottom: 0;
}

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

.exercise {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 20px;
  box-shadow: 0 6px 18px rgba(23, 32, 51, 0.04);
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.exercise:hover,
.route-card:hover {
  transform: translateY(-1px);
}

.exercise:hover {
  box-shadow: var(--shadow);
}

.exercise.done {
  border-color: rgba(38, 115, 77, 0.35);
  background: #f7fff9;
}

.exercise-header {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  align-items: start;
  margin-bottom: 8px;
}

.exercise h2 {
  margin: 6px 0 8px 0;
  font-size: 1.25rem;
  line-height: 1.25;
  letter-spacing: -0.02em;
}

.exercise p {
  margin-top: 0;
  color: var(--text);
}

.level {
  display: inline-block;
  font-size: 0.78rem;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--surface-soft);
  color: var(--primary-dark);
  font-weight: 700;
}

h3 {
  margin: 16px 0 6px 0;
  font-size: 0.98rem;
}

ul {
  margin-top: 8px;
  padding-left: 22px;
}

li {
  margin-bottom: 5px;
}

code {
  background: var(--inline-code-bg);
  padding: 2px 5px;
  border-radius: 5px;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.92em;
}

pre {
  background: var(--code-bg);
  color: var(--code-text);
  border-radius: 14px;
  padding: 16px;
  overflow-x: auto;
  margin: 12px 0;
  font-size: 0.92rem;
  line-height: 1.45;
}

pre code {
  background: transparent;
  color: inherit;
  padding: 0;
  border-radius: 0;
}

.check-label {
  white-space: nowrap;
  font-weight: 700;
  color: var(--success);
  display: inline-flex;
  align-items: center;
  gap: 7px;
  background: #edf8f1;
  border: 1px solid rgba(38, 115, 77, 0.25);
  padding: 8px 10px;
  border-radius: 999px;
}

input[type="checkbox"] {
  width: 18px;
  height: 18px;
  margin: 0;
  accent-color: var(--success);
}

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

.explanation {
  margin-top: 14px;
  border-radius: 14px;
  padding: 13px;
  background: var(--surface-soft);
  color: var(--text);
  border: 1px solid var(--border);
  display: none;
}

.explanation.visible {
  display: block;
}

.result-text {
  font-weight: 800;
  margin-bottom: 4px;
}

.result-text.correct {
  color: var(--success);
}

.result-text.wrong {
  color: var(--danger);
}

.writing-box {
  background: var(--surface-soft);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 14px;
  margin-top: 12px;
}

.empty-state,
.status,
.route-path,
.empty,
.config-note {
  color: var(--muted);
}

.topbar {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  align-items: center;
}

.status {
  font-size: 0.95rem;
}

.content-grid {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 22px;
  align-items: start;
}

.sidebar,
.content {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 20px;
  box-shadow: 0 8px 24px rgba(23, 32, 51, 0.05);
}

.section-list,
.route-list {
  display: grid;
}

.section-list {
  gap: 10px;
}

.route-list {
  gap: 12px;
}

.section-link {
  width: 100%;
  text-align: left;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 28px;
  height: 24px;
  padding: 0 8px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.18);
  color: inherit;
  font-size: 0.8rem;
}

.route-card {
  display: block;
  text-decoration: none;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px;
  background: white;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.route-card:hover {
  box-shadow: 0 10px 24px rgba(23, 32, 51, 0.08);
  border-color: rgba(31, 78, 121, 0.45);
}

.route-title {
  font-weight: 800;
  margin-bottom: 4px;
}

.route-path {
  font-size: 0.92rem;
  word-break: break-word;
}

.empty,
.error {
  padding: 14px;
  border-radius: 14px;
  background: var(--surface-soft);
}

.error {
  color: var(--danger);
  background: #fff1f1;
  border: 1px solid #f1c3c3;
}

.config-note {
  font-size: 0.92rem;
  margin-top: 12px;
}

@media (max-width: 840px) {
  .home-page header {
    padding-bottom: 62px;
  }

  .topbar,
  .content-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  main,
  .home-page main {
    padding-left: 14px;
    padding-right: 14px;
  }

  .toolbar,
  .exercise-header {
    grid-template-columns: 1fr;
  }

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

  button {
    width: 100%;
  }

  .check-label {
    width: max-content;
  }
}