/* ============================================================
   App Shell
   ============================================================ */

.app-shell {
  display: grid;
  grid-template-columns: 240px 1fr;
  min-height: 100vh;
}

.app-shell[hidden] {
  display: none;
}

@media (max-width: 780px) {
  .app-shell {
    grid-template-columns: 1fr;
    grid-template-rows: auto 1fr;
  }
  .sidebar { order: 2; }
  .main-content { order: 1; }
}

/* --- Sidebar --- */
.sidebar {
  background: var(--paper);
  border-right: 1px solid var(--paper-line);
  padding: var(--space-4) var(--space-3);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

@media (max-width: 780px) {
  .sidebar {
    border-right: none;
    border-top: 1px solid var(--paper-line);
    flex-direction: row;
    padding: var(--space-2);
    position: sticky;
    bottom: 0;
    z-index: 10;
    justify-content: space-around;
    background: var(--paper);
  }
  .sidebar .brand, .sidebar .nav-label { display: none; }
  .nav-list { display: flex; flex-direction: row; gap: var(--space-1); width: 100%; justify-content: space-around; }
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: 0 var(--space-2);
}

.brand-mark {
  width: 32px; height: 32px;
  flex-shrink: 0;
}

.brand-name {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--pen-blue);
}

.nav-list {
  list-style: none;
  margin: 0; padding: 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.nav-item a {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: var(--ink-soft);
  font-weight: 500;
  font-size: var(--text-sm);
  transition: background var(--transition-fast), color var(--transition-fast);
}

.nav-item a:hover {
  background: var(--pen-blue-light);
  color: var(--pen-blue);
}

.nav-item a.active {
  background: var(--pen-blue-light);
  color: var(--pen-blue);
  font-weight: 700;
}

.nav-item svg { width: 20px; height: 20px; flex-shrink: 0; }

@media (max-width: 780px) {
  .nav-item a { flex-direction: column; padding: var(--space-1); font-size: var(--text-xs); gap: 2px; }
}

/* --- Main content --- */
.main-content {
  padding: var(--space-4) var(--space-5);
  max-width: 1100px;
  width: 100%;
}

@media (max-width: 780px) {
  .main-content { padding: var(--space-3); }
}

.page-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: var(--space-4);
  flex-wrap: wrap;
  gap: var(--space-2);
}

.page-title {
  font-size: var(--text-2xl);
}

/* --- Stat pills (XP, Streak) in the header --- */
.stat-row {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.stat-pill {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  background: var(--paper);
  border: 1px solid var(--paper-line);
  border-radius: 999px;
  padding: var(--space-1) var(--space-3);
  box-shadow: var(--shadow-card);
}

.stat-pill .value { font-family: var(--font-mono); font-weight: 700; }
.stat-pill.xp .value { color: var(--gold); }
.stat-pill.streak .value { color: var(--brick); }

/* --- Cards --- */
.card {
  background: var(--paper);
  border: 1px solid var(--paper-line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  padding: var(--space-4);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-3);
}

/* --- Loading skeleton (perceived-speed device for the <1s goal) --- */
.skeleton {
  background: linear-gradient(90deg, var(--paper-line) 25%, #eae8dc 50%, var(--paper-line) 75%);
  background-size: 200% 100%;
  animation: skeleton-shimmer 1.2s ease-in-out infinite;
  border-radius: var(--radius-sm);
}

@keyframes skeleton-shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

@media (prefers-reduced-motion: reduce) {
  .skeleton { animation: none; background: var(--paper-line); }
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  border: none;
  border-radius: var(--radius-md);
  padding: var(--space-2) var(--space-4);
  font-weight: 600;
  font-size: var(--text-sm);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.btn:active { transform: scale(0.97); }

.btn-primary {
  background: var(--pen-blue);
  color: var(--paper);
}
.btn-primary:hover { box-shadow: var(--shadow-raised); }

.btn-ghost {
  background: transparent;
  color: var(--pen-blue);
  border: 1px solid var(--pen-blue-light);
}

.btn-ghost:hover { background: var(--pen-blue-light); }

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* --- Empty / error states --- */
.empty-state {
  text-align: center;
  padding: var(--space-6) var(--space-4);
  color: var(--ink-soft);
}

.empty-state svg { width: 48px; height: 48px; opacity: 0.4; margin-bottom: var(--space-2); }