/* ===================== Design tokens ===================== */
:root {
  --color-bg: #f7f8fc;
  --color-surface: #ffffff;
  --color-text: #1f2433;
  --color-text-muted: #6b7280;
  --color-border: #e6e8f0;

  --color-primary: #4f46e5;
  --color-primary-dark: #4338ca;
  --color-primary-light: #eef2ff;

  --color-success: #16a34a;
  --color-success-light: #dcfce7;
  --color-error: #dc2626;
  --color-error-light: #fee2e2;
  --color-warning: #d97706;
  --color-warning-light: #fef3c7;

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;

  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06);
  --shadow-md: 0 4px 16px rgba(16, 24, 40, 0.08);
  --shadow-lg: 0 12px 32px rgba(16, 24, 40, 0.12);

  --font-sans: "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }

html, body { margin: 0; padding: 0; }

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { color: var(--color-primary-dark); }

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ===================== Header ===================== */
.site-header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 50;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  font-weight: 800;
  font-size: 1.25rem;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: 8px;
}

.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--color-primary), #8b5cf6);
  color: white;
  font-weight: 800;
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 22px;
}

.main-nav a {
  color: var(--color-text-muted);
  font-weight: 600;
  font-size: 0.95rem;
}

.main-nav a:hover { color: var(--color-text); }

.nav-cta {
  background: var(--color-primary);
  color: #fff !important;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
}

.nav-cta:hover { background: var(--color-primary-dark); }

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
}

/* ===================== Layout / page ===================== */
.page {
  padding: 32px 20px 64px;
  min-height: 60vh;
}

/* ===================== Alerts / flash ===================== */
.alert {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
  font-weight: 500;
}

.alert-error { background: var(--color-error-light); color: var(--color-error); }
.alert-success { background: var(--color-success-light); color: var(--color-success); }
.alert-warning { background: var(--color-warning-light); color: var(--color-warning); }
.alert-info { background: var(--color-primary-light); color: var(--color-primary-dark); }

/* ===================== Hero ===================== */
.hero {
  text-align: center;
  padding: 64px 0 32px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.hero p {
  font-size: 1.15rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto 28px;
}

.hero-actions {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===================== Buttons ===================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-size: 0.95rem;
  border: 2px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: transform 0.05s ease, background 0.15s ease;
}

.btn:active { transform: scale(0.98); }

.btn-primary { background: var(--color-primary); color: #fff; }
.btn-primary:hover { background: var(--color-primary-dark); }

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

.btn-success { background: var(--color-success); color: #fff; }
.btn-block { width: 100%; }
.btn-sm { padding: 8px 14px; font-size: 0.85rem; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* ===================== Cards ===================== */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 20px;
  margin: 24px 0;
}

.lang-card {
  display: flex;
  flex-direction: column;
  gap: 10px;
  text-align: center;
  transition: transform 0.12s ease, box-shadow 0.12s ease;
}

.lang-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.lang-flag { font-size: 2.5rem; }
.lang-name { font-weight: 700; font-size: 1.1rem; }
.lang-native { color: var(--color-text-muted); font-size: 0.9rem; }

/* ===================== Forms ===================== */
.form-group { margin-bottom: 18px; }

label {
  display: block;
  font-weight: 600;
  margin-bottom: 6px;
  font-size: 0.9rem;
}

input, select, textarea {
  width: 100%;
  padding: 11px 14px;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
}

input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--color-primary);
}

.auth-card {
  max-width: 420px;
  margin: 40px auto;
}

.auth-card h1 { margin-top: 0; }

.muted-link { font-size: 0.9rem; color: var(--color-text-muted); margin-top: 14px; text-align: center; }

/* ===================== Dashboard ===================== */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.stat-box {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 18px;
  text-align: center;
}

.stat-value { font-size: 1.8rem; font-weight: 800; color: var(--color-primary); }
.stat-label { color: var(--color-text-muted); font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.04em; }

/* ===================== Progress ===================== */
.progress-bar {
  height: 10px;
  border-radius: 6px;
  background: var(--color-border);
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), #8b5cf6);
  border-radius: 6px;
  transition: width 0.3s ease;
}

/* ===================== Units / lessons ===================== */
.unit-block { margin-bottom: 28px; }
.unit-title { font-size: 1.2rem; font-weight: 800; margin-bottom: 12px; }

.lesson-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 14px;
}

.lesson-card {
  display: block;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 18px;
  position: relative;
}

.lesson-card.completed { border-color: var(--color-success); }
.lesson-card.completed::after {
  content: "✓";
  position: absolute;
  top: 12px;
  right: 14px;
  color: var(--color-success);
  font-weight: 800;
}

.lesson-card h3 { margin: 0 0 6px; font-size: 1rem; }
.lesson-card p { margin: 0; color: var(--color-text-muted); font-size: 0.85rem; }
.lesson-xp { display: inline-block; margin-top: 10px; font-size: 0.8rem; font-weight: 700; color: var(--color-primary); }

/* ===================== Exercise player ===================== */
.exercise-shell {
  max-width: 640px;
  margin: 0 auto;
}

.exercise-progress { margin-bottom: 24px; }

.exercise-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow-md);
  text-align: center;
}

.exercise-type-label {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 10px;
}

.exercise-prompt {
  font-size: 1.8rem;
  font-weight: 800;
  margin: 12px 0 24px;
}

.exercise-hint { color: var(--color-text-muted); font-size: 0.9rem; margin-top: -12px; margin-bottom: 20px; }

.option-list { display: flex; flex-direction: column; gap: 10px; margin: 0 0 20px; }

.option-btn {
  display: block;
  width: 100%;
  text-align: left;
  padding: 14px 18px;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.1s ease, background 0.1s ease;
}

.option-btn:hover { border-color: var(--color-primary); }
.option-btn.selected { border-color: var(--color-primary); background: var(--color-primary-light); }
.option-btn.correct { border-color: var(--color-success); background: var(--color-success-light); }
.option-btn.incorrect { border-color: var(--color-error); background: var(--color-error-light); }
.option-btn:disabled { cursor: default; }

.flashcard {
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-md);
  padding: 40px 20px;
  margin-bottom: 20px;
  cursor: pointer;
  min-height: 120px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.flashcard-back { color: var(--color-text-muted); font-size: 1.1rem; }

.feedback-box {
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  margin-bottom: 16px;
  font-weight: 700;
}

.feedback-correct { background: var(--color-success-light); color: var(--color-success); }
.feedback-incorrect { background: var(--color-error-light); color: var(--color-error); }

.srs-actions { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; }

/* ===================== Streak / XP badges ===================== */
.badge-row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.85rem;
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
}

.badge-streak { background: var(--color-warning-light); color: var(--color-warning); }

/* ===================== Admin ===================== */
.admin-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

table { width: 100%; border-collapse: collapse; margin: 16px 0; }
th, td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--color-border); font-size: 0.9rem; }
th { color: var(--color-text-muted); font-weight: 700; text-transform: uppercase; font-size: 0.75rem; letter-spacing: 0.05em; }

.tag {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 700;
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
}

/* ===================== Footer ===================== */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 24px 0;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.85rem;
}

.footer-links a { color: var(--color-text-muted); }

/* ===================== Install wizard ===================== */
.install-steps {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-bottom: 28px;
}

.install-step {
  width: 28px; height: 28px;
  border-radius: 50%;
  background: var(--color-border);
  color: var(--color-text-muted);
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.85rem;
}

.install-step.active { background: var(--color-primary); color: #fff; }
.install-step.done { background: var(--color-success); color: #fff; }

/* ===================== Responsive ===================== */
@media (max-width: 768px) {
  .main-nav {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: 14px 20px;
    gap: 14px;
  }
  .main-nav.open { display: flex; }
  .nav-toggle { display: block; }
}