*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #f7f5f0;
  --surface: #ffffff;
  --surface2: #ede9e3;
  --border: #ccc8c0;
  --text: #1e1b18;
  --text-muted: #6b6560;
  --accent: #2557a7;
  --accent-dim: #1a4080;
  --accent-light: #dde8f7;
  --success: #1a7a52;
  --success-light: #d4f0e4;
  --danger: #b83232;
  --danger-light: #fde8e8;
  --warn: #8a5c00;
  --radius: 10px;
  --sidebar-w: 280px;
  --header-h: 60px;
  --font-size: 18px;
}

body {
  font-family: Georgia, 'Times New Roman', serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: var(--font-size);
  min-height: 100vh;
}

.hidden { display: none !important; }

/* ── AUTH ─────────────────────────────────────────────────────── */

#auth-screen {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 1.5rem;
}

.auth-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2.5rem;
  width: 100%;
  max-width: 420px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.08);
}

.logo {
  text-align: center;
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 1.75rem;
  letter-spacing: -0.5px;
}

.tab-row {
  display: flex;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 1.75rem;
}

.tab-btn {
  flex: 1;
  padding: 0.75rem;
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  transition: background 0.15s, color 0.15s;
}

.tab-btn.active {
  background: var(--accent);
  color: #fff;
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.auth-form input {
  padding: 0.85rem 1rem;
  background: var(--bg);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 1rem;
  font-family: inherit;
  outline: none;
  transition: border-color 0.15s;
}

.auth-form input:focus { border-color: var(--accent); }

.auth-error {
  color: var(--danger);
  font-size: 0.9rem;
  min-height: 1.4rem;
}

/* ── ASSESSMENT ───────────────────────────────────────────────── */

#assessment-screen {
  display: flex;
  justify-content: center;
  padding: 2.5rem 1.5rem;
}

.assessment-box {
  width: 100%;
  max-width: 680px;
}

.assessment-box h2 {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
  color: var(--accent);
}

.assessment-intro {
  color: var(--text-muted);
  margin-bottom: 2rem;
  font-size: 1rem;
}

.assessment-q {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.25rem;
  transition: opacity 0.2s;
}

.assessment-q .q-text {
  font-weight: 700;
  margin-bottom: 1rem;
  font-size: 1.05rem;
}

.option-row {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.option-btn {
  text-align: left;
  padding: 0.7rem 1rem;
  border: 2px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  cursor: pointer;
  font-size: 1rem;
  font-family: inherit;
  transition: border-color 0.15s, background 0.15s;
}

.option-btn:hover { border-color: var(--accent); background: var(--accent-light); }
.option-btn.selected { border-color: var(--accent); background: var(--accent-light); color: var(--accent-dim); font-weight: 600; }

.btn-skip {
  margin-top: 0.75rem;
  padding: 0.45rem 0.9rem;
  background: transparent;
  border: 2px dashed var(--border);
  border-radius: 8px;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-family: inherit;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}
.btn-skip:hover { color: var(--text); border-color: var(--text-muted); }
.assessment-q.skipped { opacity: 0.55; }
.assessment-q.skipped .btn-skip { color: var(--warn); border-color: var(--warn); border-style: solid; }

/* ── APP SHELL ────────────────────────────────────────────────── */

#app-screen {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

.app-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0 1.5rem;
  height: var(--header-h);
  background: var(--surface);
  border-bottom: 2px solid var(--border);
  flex-shrink: 0;
}

.header-logo {
  font-weight: 700;
  color: var(--accent);
  font-size: 1.25rem;
  flex: 1;
}

.header-user {
  color: var(--text-muted);
  font-size: 0.95rem;
}

.app-layout {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* ── SIDEBAR ──────────────────────────────────────────────────── */

.sidebar {
  width: var(--sidebar-w);
  background: var(--surface);
  border-right: 2px solid var(--border);
  overflow-y: auto;
  flex-shrink: 0;
  padding-bottom: 2rem;
}

.progress-summary {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-muted);
}

.progress-bar-wrap {
  height: 6px;
  background: var(--surface2);
  border-radius: 3px;
  margin-top: 0.5rem;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 3px;
  transition: width 0.4s ease;
}

.module-header {
  padding: 1rem 1.25rem 0.4rem;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--text-muted);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.lesson-item {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.65rem 1.25rem;
  cursor: pointer;
  font-size: 0.95rem;
  color: var(--text-muted);
  border-left: 4px solid transparent;
  transition: background 0.12s, color 0.12s;
}

.lesson-item:hover { background: var(--surface2); color: var(--text); }
.lesson-item.active { border-left-color: var(--accent); background: var(--accent-light); color: var(--accent-dim); font-weight: 600; }
.lesson-item.completed { color: var(--success); }
.lesson-item.exam-lesson { font-weight: 700; }

.lesson-status-icon { font-size: 0.8rem; flex-shrink: 0; }

/* ── MAIN CONTENT ─────────────────────────────────────────────── */

.main-content {
  flex: 1;
  overflow-y: auto;
  padding: 2rem 2.5rem;
}

.panel { max-width: 740px; }

/* ── LESSON BODY ──────────────────────────────────────────────── */

.lesson-nav {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
  color: var(--text-muted);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.lesson-title {
  font-size: 1.9rem;
  font-weight: 700;
  margin-bottom: 0.4rem;
  line-height: 1.3;
}

.lesson-desc {
  color: var(--text-muted);
  margin-bottom: 2rem;
  font-size: 1rem;
}

.lesson-section { margin-bottom: 1.5rem; }

.lesson-section h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent-dim);
  margin-bottom: 0.6rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  font-size: 0.9rem;
}

.lesson-section p {
  color: var(--text);
  font-size: 1.05rem;
}

.example-block {
  background: #f0ede6;
  border-left: 4px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 1rem 1.25rem;
  font-family: 'Courier New', monospace;
  font-size: 1rem;
  white-space: pre-wrap;
  color: var(--text);
  line-height: 1.6;
}

.lesson-list {
  list-style: none;
  padding: 0;
}

.lesson-list li {
  padding: 0.4rem 0 0.4rem 1.25rem;
  position: relative;
  font-size: 1.05rem;
}

.lesson-list li::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 700;
}

.practice-block {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
}

.practice-block h4 {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--text-muted);
  margin-bottom: 1rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.practice-item {
  margin-bottom: 0.85rem;
  font-size: 1rem;
}

.practice-q { font-weight: 700; }
.practice-a { color: var(--text-muted); font-style: italic; margin-top: 0.2rem; }

.lesson-actions {
  display: flex;
  gap: 1rem;
  margin-top: 2rem;
  padding-top: 1.5rem;
  border-top: 2px solid var(--border);
  flex-wrap: wrap;
}

/* ── EXAM ─────────────────────────────────────────────────────── */

.exam-intro {
  color: var(--text-muted);
  margin-bottom: 2rem;
  font-size: 1rem;
}

.exam-q {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.25rem;
}

.exam-q-text {
  font-weight: 700;
  margin-bottom: 1rem;
  font-size: 1.05rem;
}

.exam-q-num {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 0.4rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

#exam-results {
  margin-top: 2rem;
  padding: 1.5rem;
  border-radius: var(--radius);
  border: 2px solid var(--border);
}

#exam-results.pass { border-color: var(--success); background: var(--success-light); }
#exam-results.fail { border-color: var(--danger); background: var(--danger-light); }

.result-score {
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.result-score.pass { color: var(--success); }
.result-score.fail { color: var(--danger); }

.result-breakdown { margin-top: 1.25rem; }

.result-item {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.95rem;
}

.result-item:last-child { border-bottom: none; }
.result-icon { flex-shrink: 0; font-size: 1rem; }
.result-explanation { color: var(--text-muted); font-size: 0.9rem; margin-top: 0.25rem; font-style: italic; }

/* ── BUTTONS ──────────────────────────────────────────────────── */

.btn-primary {
  padding: 0.75rem 1.5rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 700;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.15s;
}

.btn-primary:hover { background: var(--accent-dim); }
.btn-primary:disabled { opacity: 0.4; cursor: not-allowed; }

.btn-secondary {
  padding: 0.75rem 1.5rem;
  background: var(--surface);
  color: var(--text);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}

.btn-secondary:hover { background: var(--surface2); border-color: var(--text-muted); }

.btn-logout {
  padding: 0.45rem 0.9rem;
  background: transparent;
  color: var(--text-muted);
  border: 2px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
  font-family: inherit;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}

.btn-logout:hover { color: var(--danger); border-color: var(--danger); }

/* ── RESPONSIVE ───────────────────────────────────────────────── */

@media (max-width: 720px) {
  .sidebar { width: 220px; }
  .main-content { padding: 1.5rem; }
}

@media (max-width: 520px) {
  .app-layout { flex-direction: column; }
  .sidebar {
    width: 100%;
    border-right: none;
    border-bottom: 2px solid var(--border);
    max-height: 200px;
  }
  .main-content { padding: 1rem; }
  .lesson-title { font-size: 1.5rem; }
}