/* ============================================================
   EDUHUB — Master Stylesheet
   _Shared_Core/style.css  |  v2.0  |  2026-06-12
   Used by: Hub index.html, P001, P002
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap');
@import './design-tokens.css';

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

/* ── Base ─────────────────────────────────────────────────── */
html { font-size: 16px; scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
  transition: background var(--trans-slow), color var(--trans-slow);
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }
img, svg { display: block; max-width: 100%; }
button { font-family: inherit; cursor: pointer; }

/* ── Layout ───────────────────────────────────────────────── */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-6);
}

/* ── Cards ────────────────────────────────────────────────── */
.card {
  background: var(--surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  transition: box-shadow var(--trans), transform var(--trans), border-color var(--trans);
}

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

/* ── Buttons ──────────────────────────────────────────────── */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0.625rem 1.25rem;
  min-height: 44px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  transition: background var(--trans), transform var(--trans), box-shadow var(--trans);
  text-decoration: none;
}
.btn-primary:hover {
  background: var(--primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgb(99 102 241 / 0.35);
}
.btn-primary:active { transform: translateY(0); }

.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 0.625rem 1.25rem;
  min-height: 44px;
  background: var(--surface-2);
  color: var(--text);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 500;
  transition: background var(--trans), border-color var(--trans);
  text-decoration: none;
}
.btn-secondary:hover {
  background: var(--surface-3);
  border-color: var(--primary);
  color: var(--primary);
}

.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  color: var(--text);
  border: 1px solid var(--border-strong);
  transition: background var(--trans), color var(--trans);
}
.btn-icon:hover { background: var(--surface-3); color: var(--primary); }

/* ── Badges ───────────────────────────────────────────────── */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 0.2rem 0.65rem;
  border-radius: var(--radius-full);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.badge-brand   { background: var(--brand-light);   color: var(--brand); }
.badge-success { background: var(--success-light); color: var(--success); }
.badge-warning { background: var(--warning-light); color: #92400e; }
.badge-danger  { background: var(--danger-light);  color: var(--danger); }
.badge-muted   { background: var(--surface-2);     color: var(--muted); }
.dark .badge-warning { background: rgba(245,158,11,.15); color: #fbbf24; }

/* ── Language selector ────────────────────────────────────── */
.lang-selector {
  display: flex;
  gap: 2px;
  background: var(--surface-2);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  padding: 3px;
}
.lang-btn {
  padding: 0.2rem 0.55rem;
  border-radius: calc(var(--radius-sm) - 2px);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  border: none;
  background: transparent;
  color: var(--muted);
  transition: all var(--trans-fast);
  cursor: pointer;
}
.lang-btn.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 1px 4px rgb(0 0 0 / 0.15);
}
.lang-btn:not(.active):hover { background: var(--surface-3); color: var(--text); }

/* ── Progress bar ─────────────────────────────────────────── */
.progress-bar {
  height: 0.45rem;
  background: var(--surface-2);
  border-radius: var(--radius-full);
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--primary-hover));
  border-radius: var(--radius-full);
  transition: width 0.5s ease;
}

/* ── Quiz: question grid buttons ──────────────────────────── */
.q-btn {
  width: 2.75rem;
  height: 2.75rem;
  border-radius: var(--radius-xs);
  font-weight: 600;
  font-size: 0.8rem;
  border: 1.5px solid var(--border-strong);
  background: var(--surface);
  color: var(--muted);
  transition: all var(--trans-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}
.q-btn:hover            { border-color: var(--primary); color: var(--primary); }
.q-btn.active           { border-color: var(--primary); background: var(--primary-light); color: var(--primary); }
.q-btn.answered         { border-color: var(--primary); background: var(--primary); color: #fff; }
.q-btn.correct-answered { border-color: var(--success); background: var(--success); color: #fff; }
.q-btn.wrong-answered   { border-color: var(--danger);  background: var(--danger);  color: #fff; }

/* ── Quiz: answer options ─────────────────────────────────── */
.option {
  padding: 0.9rem 1rem;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--trans);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.9rem;
}
.option:hover    { border-color: var(--primary); background: var(--primary-light); }
.option.selected { border-color: var(--primary); background: var(--primary-light); }
.option.correct  { border-color: var(--success); background: var(--success-light); }
.option.wrong    { border-color: var(--danger);  background: var(--danger-light); }
.dark .option.correct { background: rgba(16,185,129,.12); }
.dark .option.wrong   { background: rgba(239,68,68,.1); }

/* ── Tabs ─────────────────────────────────────────────────── */
.tab {
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-sm);
  font-weight: 500;
  font-size: 0.85rem;
  cursor: pointer;
  border: none;
  background: transparent;
  color: var(--muted);
  transition: all var(--trans-fast);
}
.tab.active { background: var(--primary-light); color: var(--primary); font-weight: 600; }
.tab:not(.active):hover { background: var(--surface-2); color: var(--text); }

/* ── Wrong answers summary ────────────────────────────────── */
.wrong-summary-title {
  font-size: 0.7rem; font-weight: 800; text-transform: uppercase;
  letter-spacing: 0.07em; color: var(--danger); margin-bottom: 0.5rem;
}
.wrong-item {
  display: flex; align-items: center; gap: 0.65rem;
  padding: 0.5rem 0.75rem; border-radius: var(--radius-sm);
  border: 1px solid rgba(239,68,68,.2);
  background: var(--danger-light);
  margin-bottom: 0.35rem;
}
.wrong-item-num  { font-weight: 800; font-size: 0.78rem; color: var(--danger); flex-shrink: 0; min-width: 1.8rem; }
.wrong-item-text { font-size: 0.78rem; color: var(--text); flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.wrong-item-answers { display: flex; gap: 0.3rem; align-items: center; flex-shrink: 0; }
.wrong-item-user    { background: rgba(239,68,68,.2); color: var(--danger); padding: 0.1rem 0.45rem; border-radius: 0.3rem; font-weight: 800; font-size: 0.75rem; }
.wrong-item-correct { background: var(--success-light); color: var(--success); padding: 0.1rem 0.45rem; border-radius: 0.3rem; font-weight: 800; font-size: 0.75rem; }
.wrong-item-arrow   { color: var(--muted); font-size: 0.7rem; }
.dark .wrong-item   { background: rgba(239,68,68,.08); }

/* ── Number line SVG ──────────────────────────────────────── */
.number-line { width: 100%; height: 80px; }

/* ── Cards grid ───────────────────────────────────────────── */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-6);
}

/* ── Animations ───────────────────────────────────────────── */
.fade-in { animation: fadeIn 0.35s ease both; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(40px); }
  to   { opacity: 1; transform: translateX(0); }
}
@keyframes slideInLeft {
  from { opacity: 0; transform: translateX(-40px); }
  to   { opacity: 1; transform: translateX(0); }
}
.slide-in-right { animation: slideInRight 0.25s cubic-bezier(.25,.46,.45,.94) both; }
.slide-in-left  { animation: slideInLeft  0.25s cubic-bezier(.25,.46,.45,.94) both; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

/* ── KaTeX ────────────────────────────────────────────────── */
.katex-display { margin: 0.5em 0; overflow-x: auto; overflow-y: hidden; }

/* ── Responsive ───────────────────────────────────────────── */
@media (max-width: 1024px) {
  .container { padding: 0 var(--space-4); }
  .card-grid { grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
}
@media (max-width: 768px) {
  .container { padding: 0 var(--space-3); }
  .card-grid { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .container { padding: 0 var(--space-2); }
  .q-btn     { width: 2.25rem; height: 2.25rem; font-size: 0.72rem; }
}
@media (max-width: 480px) {
  body   { font-size: 0.9rem; }
  .card  { border-radius: var(--radius); }
  .badge { font-size: 0.65rem; }
}