/* ── Reset & Base ─────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --green-900: #1B4332;
  --green-700: #2D6A4F;
  --green-500: #40916C;
  --green-400: #52B788;
  --green-200: #B7E4C7;
  --green-100: #D8F3DC;
  --green-50:  #F0FAF2;
  --gold:      #C9A84C;
  --gold-light:#F5E6B2;
  --text-dark: #1A2E1E;
  --text-mid:  #3D5A46;
  --text-light:#6B8F71;
  --white:     #FFFFFF;
  --card-shadow: 0 4px 20px rgba(27,67,50,0.12);
  --card-shadow-hover: 0 8px 32px rgba(27,67,50,0.2);
  --radius: 16px;
  --transition: 0.25s ease;
}

html { font-size: 16px; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--green-50);
  color: var(--text-dark);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ── Header ───────────────────────────────────────── */
header {
  background: linear-gradient(135deg, var(--green-900) 0%, var(--green-700) 100%);
  color: var(--white);
  padding: 1.25rem 2rem;
  box-shadow: 0 2px 12px rgba(0,0,0,0.2);
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  background: rgba(255,255,255,0.1);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid rgba(255,255,255,0.2);
}

.header-text h1 {
  font-size: 1.6rem;
  font-weight: 800;
  letter-spacing: -0.5px;
  color: var(--white);
}

.header-text p {
  font-size: 0.8rem;
  color: var(--green-200);
  margin-top: 2px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  font-weight: 500;
}

/* ── Tab Navigation ───────────────────────────────── */
.tabs-nav {
  background: var(--green-900);
  border-bottom: 1px solid rgba(255,255,255,0.08);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

.tabs-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  gap: 4px;
  padding: 0 1rem;
  overflow-x: auto;
  scrollbar-width: none;
}

.tabs-inner::-webkit-scrollbar { display: none; }

.tab-btn {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.75rem 1.25rem;
  background: transparent;
  border: none;
  color: var(--green-200);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  transition: all var(--transition);
  white-space: nowrap;
  position: relative;
  top: 1px;
}

.tab-btn .tab-icon { font-size: 1rem; }

.tab-btn:hover {
  color: var(--white);
  background: rgba(255,255,255,0.06);
}

.tab-btn.active {
  color: var(--white);
  border-bottom-color: var(--gold);
  background: rgba(255,255,255,0.08);
}

/* ── Main Content ─────────────────────────────────── */
main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1.5rem 3rem;
  flex: 1;
  width: 100%;
}

/* ── Session Header ───────────────────────────────── */
.session-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 2rem;
  gap: 1rem;
  flex-wrap: wrap;
}

#tab-title {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--green-900);
  letter-spacing: -0.5px;
}

#tab-subtitle {
  font-size: 0.875rem;
  color: var(--text-light);
  margin-top: 0.25rem;
}

.shuffle-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  background: var(--green-700);
  color: var(--white);
  border: none;
  border-radius: 10px;
  font-size: 0.875rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
  letter-spacing: 0.2px;
  box-shadow: 0 2px 8px rgba(45,106,79,0.3);
  white-space: nowrap;
}

.shuffle-btn:hover {
  background: var(--green-900);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(27,67,50,0.35);
}

.shuffle-btn:active { transform: translateY(0); }

.shuffle-btn svg { transition: transform 0.5s ease; }
.shuffle-btn:hover svg { transform: rotate(180deg); }

/* ── Cards Grid ───────────────────────────────────── */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

/* ── Card Flip ────────────────────────────────────── */
.card-wrapper {
  perspective: 1200px;
  height: 280px;
  cursor: pointer;
}

.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.4, 0.2, 0.2, 1);
}

.card-wrapper.flipped .card-inner {
  transform: rotateY(180deg);
}

.card-front,
.card-back {
  position: absolute;
  inset: 0;
  border-radius: var(--radius);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
}

/* Front face */
.card-front {
  background: var(--white);
  box-shadow: var(--card-shadow);
  border: 1px solid rgba(27,67,50,0.07);
  transition: box-shadow var(--transition);
}

.card-wrapper:hover .card-front {
  box-shadow: var(--card-shadow-hover);
}

.card-category-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--green-500);
  background: var(--green-100);
  padding: 0.25rem 0.6rem;
  border-radius: 20px;
  margin-bottom: 1rem;
  width: fit-content;
}

.card-front h3 {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--green-900);
  line-height: 1.3;
  margin-bottom: 0.75rem;
  letter-spacing: -0.3px;
}

.card-description {
  font-size: 0.875rem;
  color: var(--text-mid);
  line-height: 1.65;
  flex: 1;
}

.flip-hint {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.72rem;
  color: var(--text-light);
  margin-top: 1rem;
  font-weight: 500;
  letter-spacing: 0.2px;
}

.flip-hint svg {
  opacity: 0.6;
}

/* Back face */
.card-back {
  background: linear-gradient(145deg, var(--green-700) 0%, var(--green-900) 100%);
  box-shadow: var(--card-shadow);
  transform: rotateY(180deg);
  color: var(--white);
  justify-content: space-between;
}

.back-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.back-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--gold);
  background: rgba(201, 168, 76, 0.15);
  padding: 0.25rem 0.6rem;
  border-radius: 20px;
  border: 1px solid rgba(201,168,76,0.3);
}

.card-back h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--green-100);
  margin-bottom: 0.75rem;
}

.card-improvement {
  font-size: 0.875rem;
  color: rgba(255,255,255,0.85);
  line-height: 1.65;
  flex: 1;
}

.back-flip-hint {
  font-size: 0.72rem;
  color: rgba(255,255,255,0.4);
  margin-top: 1rem;
  font-weight: 500;
}

/* ── Drill Count Selector ─────────────────────────── */
.drill-count-selector {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.drill-count-selector label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.count-buttons {
  display: flex;
  gap: 0.4rem;
}

.count-btn {
  padding: 0.35rem 0.75rem;
  border: 2px solid var(--green-200);
  border-radius: 8px;
  background: var(--white);
  color: var(--text-mid);
  font-size: 0.8rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
}

.count-btn:hover {
  border-color: var(--green-400);
  color: var(--green-700);
}

.count-btn.active {
  background: var(--green-700);
  border-color: var(--green-700);
  color: var(--white);
}

/* ── Loading State ────────────────────────────────── */
.loading {
  grid-column: 1 / -1;
  text-align: center;
  padding: 3rem;
  color: var(--text-light);
  font-size: 0.9rem;
}

/* ── Footer ───────────────────────────────────────── */
footer {
  background: var(--green-900);
  color: var(--green-200);
  text-align: center;
  padding: 1.25rem;
  font-size: 0.8rem;
  letter-spacing: 0.3px;
}

/* ── Responsive ───────────────────────────────────── */
@media (max-width: 768px) {
  .header-inner { padding: 0; }
  .header-text h1 { font-size: 1.3rem; }
  main { padding: 1.5rem 1rem 2.5rem; }
  .cards-grid { grid-template-columns: 1fr; gap: 1rem; }
  .card-wrapper { height: 300px; }
  .session-header { flex-direction: column; }
  .tab-label { display: none; }
  .tab-btn { padding: 0.75rem 1rem; }
  .tab-btn .tab-icon { font-size: 1.2rem; }
}

@media (max-width: 480px) {
  header { padding: 1rem; }
  .logo { display: none; }
}

/* ── Header Auth Area ─────────────────────────────────────────── */

.header-auth {
  display: flex;
  align-items: center;
  flex-shrink: 0;
  margin-left: auto;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.user-info[hidden] { display: none; }

.user-avatar {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  border: 2px solid rgba(255,255,255,0.35);
  object-fit: cover;
  flex-shrink: 0;
}

.user-name {
  color: var(--white);
  font-size: 0.85rem;
  font-weight: 600;
  max-width: 100px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.icon-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.2);
  border-radius: 8px;
  color: var(--white);
  cursor: pointer;
  transition: all var(--transition);
  flex-shrink: 0;
}

.icon-btn:hover {
  background: rgba(255,255,255,0.22);
}

.signout-btn {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.35rem 0.75rem;
  background: rgba(255,255,255,0.1);
  border: 1px solid rgba(255,255,255,0.2);
  border-radius: 8px;
  color: var(--green-200);
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}

.signout-btn:hover {
  background: rgba(255,255,255,0.2);
  color: var(--white);
}

@media (max-width: 600px) {
  .user-name { display: none; }
}

/* ── Card Overflow Menu ───────────────────────────────────────── */
.overflow-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  width: 28px;
  height: 28px;
  background: rgba(255,255,255,0.9);
  border: 1px solid var(--green-100);
  border-radius: 6px;
  color: var(--text-mid);
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
  opacity: 0;
  transition: opacity var(--transition), background var(--transition);
}

.card-wrapper:hover .overflow-btn {
  opacity: 1;
}

.overflow-btn:hover {
  background: var(--white);
  color: var(--green-900);
}

.overflow-menu {
  position: absolute;
  top: 2.75rem;
  right: 0.5rem;
  background: var(--white);
  border: 1px solid var(--green-100);
  border-radius: 10px;
  box-shadow: 0 4px 20px rgba(27,67,50,0.18);
  z-index: 20;
  min-width: 170px;
  display: none;
  overflow: hidden;
}

.overflow-menu.open {
  display: block;
}

.overflow-item {
  display: block;
  width: 100%;
  padding: 0.7rem 1rem;
  background: none;
  border: none;
  text-align: left;
  font-size: 0.85rem;
  color: var(--text-dark);
  cursor: pointer;
  transition: background var(--transition);
}

.overflow-item:hover {
  background: var(--green-50);
  color: var(--green-900);
}

/* ── Empty state ─────────────────────────────────────────────── */
.empty-state {
  grid-column: 1 / -1;
  text-align: center;
  padding: 3rem 1rem;
  color: var(--text-light);
  font-size: 0.9rem;
}

.link-btn {
  background: none;
  border: none;
  color: var(--green-500);
  font-size: inherit;
  font-weight: 600;
  cursor: pointer;
  text-decoration: underline;
  padding: 0;
}

.link-btn:hover { color: var(--green-700); }

/* ── Preferences Modal ───────────────────────────────────────── */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.45);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.modal-overlay[hidden] { display: none; }

.modal {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: 0 20px 60px rgba(0,0,0,0.25);
  width: 100%;
  max-width: 480px;
  max-height: 85vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--green-100);
}

.modal-header h3 {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--green-900);
  letter-spacing: -0.3px;
}

.modal-close {
  width: 30px;
  height: 30px;
  background: var(--green-50);
  border: 1px solid var(--green-100);
  border-radius: 8px;
  color: var(--text-mid);
  font-size: 0.85rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
}

.modal-close:hover {
  background: var(--green-100);
  color: var(--green-900);
}

.modal-body {
  padding: 1.5rem;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
}

.prefs-section { display: flex; flex-direction: column; gap: 0.6rem; }

.prefs-section-title {
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--green-900);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.prefs-hint {
  font-size: 0.8rem;
  color: var(--text-light);
  line-height: 1.5;
}

/* ── Hidden Drills List ──────────────────────────────────────── */
.hidden-drills-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.hidden-drill-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.65rem 0.85rem;
  background: var(--green-50);
  border: 1px solid var(--green-100);
  border-radius: 10px;
}

.hidden-drill-title {
  font-size: 0.85rem;
  color: var(--text-dark);
  font-weight: 500;
  flex: 1;
  line-height: 1.4;
}

.unhide-btn {
  flex-shrink: 0;
  padding: 0.3rem 0.7rem;
  background: var(--green-700);
  border: none;
  border-radius: 6px;
  color: var(--white);
  font-size: 0.75rem;
  font-weight: 700;
  cursor: pointer;
  transition: background var(--transition);
}

.unhide-btn:hover { background: var(--green-900); }

/* ── Toast Notification ──────────────────────────────────────── */
.toast {
  position: fixed;
  bottom: 1.5rem;
  left: 50%;
  transform: translateX(-50%);
  padding: 0.75rem 1.25rem;
  border-radius: 10px;
  font-size: 0.875rem;
  font-weight: 600;
  z-index: 300;
  box-shadow: 0 4px 16px rgba(0,0,0,0.2);
  white-space: nowrap;
}

.toast[hidden] { display: none; }

.toast-error {
  background: #fff1f0;
  border: 1px solid #ffccc7;
  color: #a8071a;
}

.toast-success {
  background: var(--green-100);
  border: 1px solid var(--green-200);
  color: var(--green-900);
}

/* ── Gate Screens (welcome + not-authorized) ─────────────────── */
.gate-screen {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem 1rem;
  background: linear-gradient(160deg, var(--green-900) 0%, var(--green-700) 55%, var(--green-500) 100%);
  min-height: 0; /* let flex parent control height */
}

.gate-screen[hidden] { display: none; }

.gate-card {
  background: var(--white);
  border-radius: 24px;
  padding: 2.75rem 2.25rem;
  max-width: 400px;
  width: 100%;
  text-align: center;
  box-shadow: 0 32px 80px rgba(0,0,0,0.3), 0 0 0 1px rgba(255,255,255,0.08);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.gate-logo {
  width: 72px;
  height: 72px;
  background: var(--green-100);
  border: 2px solid var(--green-200);
  border-radius: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.5rem;
}

.gate-icon-large {
  font-size: 3rem;
  margin-bottom: 1.25rem;
  line-height: 1;
}

.gate-card h2 {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--green-900);
  letter-spacing: -0.5px;
  margin-bottom: 0.5rem;
}

.gate-tagline {
  font-size: 0.95rem;
  color: var(--text-mid);
  font-weight: 500;
  margin-bottom: 1rem;
  line-height: 1.5;
}

.gate-description {
  font-size: 0.85rem;
  color: var(--text-light);
  line-height: 1.65;
  margin-bottom: 1.75rem;
}

.gate-signin-area {
  display: flex;
  justify-content: center;
  margin-bottom: 1.25rem;
}

.gate-access-note {
  font-size: 0.75rem;
  color: var(--text-light);
  letter-spacing: 0.2px;
}

.gate-secondary-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.65rem 1.25rem;
  background: var(--green-50);
  border: 1.5px solid var(--green-200);
  border-radius: 10px;
  color: var(--green-700);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  margin-top: 0.5rem;
}

.gate-secondary-btn:hover {
  background: var(--green-100);
  border-color: var(--green-400);
  color: var(--green-900);
}

@media (max-width: 480px) {
  .gate-card { padding: 2rem 1.5rem; }
  .gate-card h2 { font-size: 1.5rem; }
}