:root {
  --bg: #0f172a;
  --bg-alt: #1e293b;
  --card: #1e293b;
  --card-alt: #273449;
  --border: #334155;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --primary: #38bdf8;
  --primary-strong: #0ea5e9;
  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.15);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.15);
  --warning: #f59e0b;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  min-height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

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

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

header.app-header {
  background: var(--bg-alt);
  border-bottom: 1px solid var(--border);
  padding: 1rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

header.app-header h1 {
  margin: 0;
  font-size: 1.25rem;
  font-weight: 600;
}

header.app-header .header-actions {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

header.app-header .header-actions a {
  font-size: 0.85rem;
  color: var(--muted);
  margin-left: 1rem;
}

header.app-header .header-actions a.header-btn {
  margin-left: 0;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text);
  padding: 0.55rem 1rem;
  border-radius: 8px;
  background: var(--card-alt);
  border: 1px solid var(--border);
  transition: transform 0.1s ease, background 0.15s ease, border-color 0.15s ease;
  text-decoration: none;
  white-space: nowrap;
}

header.app-header .header-actions a.header-btn:hover {
  background: var(--card);
  border-color: var(--primary);
  text-decoration: none;
  transform: translateY(-1px);
}

header.app-header .header-actions a.header-btn.primary {
  background: var(--primary);
  color: #0f172a;
  border-color: var(--primary);
  font-weight: 600;
}

header.app-header .header-actions a.header-btn.primary:hover {
  background: var(--primary-strong);
  border-color: var(--primary-strong);
  color: #0f172a;
}

@media (max-width: 540px) {
  header.app-header { flex-direction: column; gap: 0.75rem; align-items: flex-start; }
  header.app-header .header-actions { width: 100%; }
}

h1, h2, h3 { color: #f8fafc; }

.subtitle {
  color: var(--muted);
  margin-top: -0.5rem;
  margin-bottom: 2rem;
}

.subject-list {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
}

.subject-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem;
  cursor: pointer;
  transition: transform 0.15s ease, border-color 0.15s ease;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.subject-card:hover { transform: translateY(-2px); border-color: var(--primary); }

.subject-card h3 { margin: 0; font-size: 1.1rem; }
.subject-card .meta { color: var(--muted); font-size: 0.875rem; }

.subject-card .resume-pill {
  margin-top: 0.5rem;
  display: inline-block;
  background: var(--success-bg);
  color: var(--success);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.25rem 0.5rem;
  border-radius: 999px;
}

.empty-state {
  background: var(--card);
  border: 1px dashed var(--border);
  border-radius: 12px;
  padding: 2.5rem 1.5rem;
  text-align: center;
  color: var(--muted);
}

.empty-state strong { color: var(--text); display: block; margin-bottom: 0.5rem; }

.test-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.test-progress {
  color: var(--muted);
  font-size: 0.9rem;
}

.progress-bar {
  height: 8px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 2rem;
}

.progress-bar .fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--primary-strong));
  transition: width 0.3s ease;
}

.question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
}

.question-statement {
  font-size: 1.1rem;
  margin-bottom: 1.5rem;
  white-space: pre-wrap;
}

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

.option {
  display: block;
  text-align: left;
  padding: 0.875rem 1rem;
  background: var(--card-alt);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  cursor: pointer;
  font: inherit;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.option:hover:not(:disabled) { border-color: var(--primary); }
.option:disabled { cursor: not-allowed; opacity: 0.85; }

.option.selected.correct {
  background: var(--success-bg);
  border-color: var(--success);
  color: #bbf7d0;
}

.option.selected.wrong {
  background: var(--danger-bg);
  border-color: var(--danger);
  color: #fecaca;
}

.option.reveal-correct {
  background: var(--success-bg);
  border-color: var(--success);
  color: #bbf7d0;
}

.feedback {
  margin-top: 1.25rem;
  padding: 1rem;
  border-radius: 8px;
  background: var(--card-alt);
  border-left: 4px solid var(--primary);
}

.feedback.correct { border-color: var(--success); }
.feedback.wrong { border-color: var(--danger); }

.feedback strong { display: block; margin-bottom: 0.25rem; }
.feedback .muted { color: var(--muted); font-size: 0.875rem; }

.test-actions {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 1.5rem;
}

button.primary, .btn-primary {
  background: var(--primary);
  color: #0f172a;
  border: none;
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
  font-size: 1rem;
}

button.primary:hover, .btn-primary:hover { background: var(--primary-strong); }
button.primary:disabled { opacity: 0.5; cursor: not-allowed; }

button.secondary, .btn-secondary {
  background: transparent;
  color: var(--muted);
  border: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  cursor: pointer;
  font-size: 1rem;
}

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

.btn-danger {
  background: transparent;
  color: var(--danger);
  border: 1px solid var(--danger);
  padding: 0.5rem 1rem;
  border-radius: 8px;
  cursor: pointer;
}

.btn-danger:hover { background: var(--danger-bg); }

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}

.stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem;
  text-align: center;
}

.stat-card .value {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary);
  line-height: 1;
}

.stat-card.correct .value { color: var(--success); }
.stat-card.wrong .value { color: var(--danger); }

.stat-card .label {
  color: var(--muted);
  margin-top: 0.5rem;
  font-size: 0.875rem;
}

.loading { color: var(--muted); padding: 2rem; text-align: center; }

.error-message {
  background: var(--danger-bg);
  border: 1px solid var(--danger);
  color: #fecaca;
  padding: 1rem;
  border-radius: 8px;
  margin: 1rem 0;
}

.toolbar {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  align-items: center;
}

.toolbar input[type="text"] {
  flex: 1;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.625rem 0.875rem;
  color: var(--text);
  font: inherit;
}

@media (max-width: 600px) {
  .container { padding: 1rem; }
  .question-statement { font-size: 1rem; }
  .stat-card .value { font-size: 2rem; }
}

.tabs {
  display: flex;
  gap: 0.25rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 1.5rem;
}

.tabs .tab {
  background: transparent;
  border: 0;
  color: var(--muted);
  padding: 0.75rem 1.25rem;
  font: inherit;
  font-size: 1rem;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.tabs .tab:hover { color: var(--text); }

.tabs .tab.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
  font-weight: 600;
}

/* Cabecera de sección de grado/curso en la home */
.course-section-title {
  grid-column: 1 / -1;
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.4rem;
  margin: 1.25rem 0 0.25rem;
}

.questions-list {
  display: flex;
  flex-direction: column;
  gap: 0.875rem;
}

.question-row {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.25rem;
}

.question-row .stm {
  font-weight: 600;
  margin-bottom: 0.875rem;
  white-space: pre-wrap;
  display: flex;
  gap: 0.5rem;
}

.question-row .stm .num {
  color: var(--muted);
  font-weight: 400;
  flex-shrink: 0;
}

.question-row ul.opts {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.question-row ul.opts li {
  background: var(--card-alt);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.6rem 0.875rem;
  display: flex;
  align-items: flex-start;
  gap: 0.6rem;
  color: var(--muted);
}

.question-row ul.opts li.correct {
  background: var(--success-bg);
  border-color: var(--success);
  color: #d1fae5;
  font-weight: 600;
}

.question-row ul.opts li .mark {
  flex-shrink: 0;
  font-weight: 700;
  width: 1.2em;
  text-align: center;
}

.question-row ul.opts li.correct .mark { color: var(--success); }
.question-row ul.opts li:not(.correct) .mark { color: var(--muted); opacity: 0.5; }

.questions-toolbar {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 1rem;
}

.questions-toolbar input[type="search"] {
  flex: 1;
  min-width: 200px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.625rem 0.875rem;
  color: var(--text);
  font: inherit;
}

.questions-toolbar input[type="search"]:focus {
  outline: none;
  border-color: var(--primary);
}

/* === Barra de filtros (grado + comunidad) === */
.filter-bar {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  margin: 0.75rem 0 1.5rem;
  padding: 0.625rem 1rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.filter-group {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.filter-group label {
  color: var(--muted);
  font-size: 0.85rem;
  white-space: nowrap;
}

.filter-group select {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.35rem 0.65rem;
  color: var(--text);
  font: inherit;
  font-size: 0.9rem;
  cursor: pointer;
}

.filter-group select:focus {
  outline: none;
  border-color: var(--primary);
}

/* separador vertical entre filtros */
.filter-group + .filter-group::before {
  content: '';
  display: block;
  width: 1px;
  height: 1.2em;
  background: var(--border);
  margin-right: 0.5rem;
}

/* === Barra de donaciones === */
.donate-bar {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  flex-wrap: wrap;
  margin: 0 0 1.5rem;
  padding: 0.75rem 1.1rem;
  background: rgba(245, 158, 11, 0.07);
  border: 1px solid rgba(245, 158, 11, 0.35);
  border-radius: 10px;
}

.donate-label {
  color: #fcd34d;
  font-size: 0.9rem;
  flex: 1;
  min-width: 160px;
}

.donate-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.42rem 0.9rem;
  border-radius: 6px;
  font: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  transition: opacity 0.15s;
  white-space: nowrap;
}

.donate-btn:hover { opacity: 0.82; text-decoration: none; }

.donate-btn.paypal {
  background: #003087;
  color: #fff;
}

.donate-bizum {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--muted);
  font-size: 0.875rem;
  white-space: nowrap;
}

@media (max-width: 540px) {
  .donate-bar { gap: 0.6rem; }
  .donate-label { flex-basis: 100%; margin-bottom: 0.1rem; }
}