/* ============================================================
   VYLEX NEXYS EdTech — Design System
   Premium dark-mode glassmorphism UI
   ============================================================ */

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

:root {
  /* Core palette */
  --bg-base: #0a0e1a;
  --bg-surface: #0f172a;
  --bg-elevated: #1e293b;
  --bg-glass: rgba(30, 41, 59, 0.65);
  --bg-glass-hover: rgba(30, 41, 59, 0.85);
  --border-subtle: rgba(255,255,255,0.06);
  --border-default: rgba(255,255,255,0.1);
  --border-strong: rgba(255,255,255,0.18);
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --text-inverse: #0f172a;

  /* Brand */
  --brand-400: #a78bfa;
  --brand-500: #8b5cf6;
  --brand-600: #7c3aed;
  --brand-700: #6d28d9;
  --brand-900: #4c1d95;
  --brand-glow: rgba(124, 58, 237, 0.35);

  /* Subject colors */
  --et-math: #8b5cf6;
  --et-physics: #3b82f6;
  --et-chemistry: #06b6d4;
  --et-lifesci: #10b981;
  --et-cat: #f59e0b;
  --et-egd: #ef4444;
  --et-agrisci: #84cc16;

  /* Semantic */
  --success: #10b981;
  --error: #ef4444;
  --warning: #f59e0b;
  --info: #3b82f6;

  /* Typography */
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-display: 'Outfit', 'Inter', sans-serif;
  --fs-xs: 0.6875rem;
  --fs-sm: 0.8125rem;
  --fs-base: 0.9375rem;
  --fs-lg: 1.125rem;
  --fs-xl: 1.375rem;
  --fs-2xl: 1.75rem;
  --fs-3xl: 2.25rem;
  --fs-4xl: 3rem;

  /* Spacing */
  --sp-1: 0.25rem; --sp-2: 0.5rem; --sp-3: 0.75rem; --sp-4: 1rem;
  --sp-5: 1.25rem; --sp-6: 1.5rem; --sp-8: 2rem; --sp-10: 2.5rem;
  --sp-12: 3rem; --sp-16: 4rem; --sp-20: 5rem;

  /* Radii */
  --r-sm: 0.5rem; --r-md: 0.75rem; --r-lg: 1rem;
  --r-xl: 1.25rem; --r-2xl: 1.5rem; --r-full: 9999px;

  /* Transitions */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --t-fast: 150ms; --t-base: 250ms; --t-slow: 400ms;
}

html { font-size: 16px; -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--font-body);
  background: var(--bg-base);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-tap-highlight-color: transparent;
  overflow-x: hidden;
  min-height: 100dvh;
}

::-webkit-scrollbar { width: 0; height: 0; background: transparent; }

img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { cursor: pointer; border: none; background: none; font: inherit; color: inherit; }
input { font: inherit; color: inherit; }

/* --- Typography --- */
.font-display { font-family: var(--font-display); }
.text-xs { font-size: var(--fs-xs); }
.text-sm { font-size: var(--fs-sm); }
.text-base { font-size: var(--fs-base); }
.text-lg { font-size: var(--fs-lg); }
.text-xl { font-size: var(--fs-xl); }
.text-2xl { font-size: var(--fs-2xl); }
.text-3xl { font-size: var(--fs-3xl); }
.text-4xl { font-size: var(--fs-4xl); }
.font-medium { font-weight: 500; }
.font-bold { font-weight: 700; }
.font-extrabold { font-weight: 800; }
.tracking-tight { letter-spacing: -0.02em; }
.text-center { text-align: center; }
.text-muted { color: var(--text-secondary); }
.text-brand { color: var(--brand-400); }
.text-white { color: #fff; }
.uppercase { text-transform: uppercase; }

.gradient-text {
  background: linear-gradient(135deg, #a78bfa 0%, #38bdf8 50%, #34d399 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* --- Layout --- */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.flex-1 { flex: 1; }
.items-center { align-items: center; }
.items-end { align-items: flex-end; }
.items-start { align-items: flex-start; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: var(--sp-1); }
.gap-2 { gap: var(--sp-2); }
.gap-3 { gap: var(--sp-3); }
.gap-4 { gap: var(--sp-4); }
.gap-6 { gap: var(--sp-6); }
.gap-8 { gap: var(--sp-8); }
.w-full { width: 100%; }
.max-w-sm { max-width: 26rem; }
.max-w-md { max-width: 32rem; }
.max-w-lg { max-width: 40rem; }
.max-w-4xl { max-width: 56rem; }
.mx-auto { margin-left: auto; margin-right: auto; }
.relative { position: relative; }
.absolute { position: absolute; }
.fixed { position: fixed; }
.inset-0 { top: 0; right: 0; bottom: 0; left: 0; }
.z-10 { z-index: 10; }
.z-20 { z-index: 20; }
.z-30 { z-index: 30; }
.z-50 { z-index: 50; }
.overflow-hidden { overflow: hidden; }
.overflow-y-auto { overflow-y: auto; }
.overflow-x-auto { overflow-x: auto; }
.shrink-0 { flex-shrink: 0; }

/* --- Spacing --- */
.p-2 { padding: var(--sp-2); }
.p-3 { padding: var(--sp-3); }
.p-4 { padding: var(--sp-4); }
.p-5 { padding: var(--sp-5); }
.p-6 { padding: var(--sp-6); }
.px-3 { padding-left: var(--sp-3); padding-right: var(--sp-3); }
.px-4 { padding-left: var(--sp-4); padding-right: var(--sp-4); }
.px-5 { padding-left: var(--sp-5); padding-right: var(--sp-5); }
.px-6 { padding-left: var(--sp-6); padding-right: var(--sp-6); }
.px-8 { padding-left: var(--sp-8); padding-right: var(--sp-8); }
.py-2 { padding-top: var(--sp-2); padding-bottom: var(--sp-2); }
.py-3 { padding-top: var(--sp-3); padding-bottom: var(--sp-3); }
.py-4 { padding-top: var(--sp-4); padding-bottom: var(--sp-4); }
.py-6 { padding-top: var(--sp-6); padding-bottom: var(--sp-6); }
.pt-4 { padding-top: var(--sp-4); }
.pt-8 { padding-top: var(--sp-8); }
.pt-10 { padding-top: var(--sp-10); }
.pt-20 { padding-top: var(--sp-20); }
.pb-6 { padding-bottom: var(--sp-6); }
.pb-24 { padding-bottom: 6rem; }
.mb-1 { margin-bottom: var(--sp-1); }
.mb-2 { margin-bottom: var(--sp-2); }
.mb-3 { margin-bottom: var(--sp-3); }
.mb-4 { margin-bottom: var(--sp-4); }
.mb-6 { margin-bottom: var(--sp-6); }
.mb-8 { margin-bottom: var(--sp-8); }
.mb-10 { margin-bottom: var(--sp-10); }
.mt-1 { margin-top: var(--sp-1); }
.mt-4 { margin-top: var(--sp-4); }
.mt-auto { margin-top: auto; }

/* Grid */
.grid { display: grid; }
.grid-cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid-cols-3 { grid-template-columns: repeat(3, 1fr); }
.col-span-2 { grid-column: span 2; }

@media (min-width: 640px) {
  .sm-grid-cols-2 { grid-template-columns: repeat(2, 1fr); }
  .sm-grid-cols-3 { grid-template-columns: repeat(3, 1fr); }
}

/* --- Components --- */

/* Glass Card */
.glass-card {
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-default);
  border-radius: var(--r-xl);
  transition: border-color var(--t-base) var(--ease-out),
              transform var(--t-base) var(--ease-out),
              box-shadow var(--t-base) var(--ease-out);
}

.glass-card:hover {
  border-color: var(--border-strong);
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}

.glass-card-static {
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-default);
  border-radius: var(--r-xl);
}

/* Subject Card */
.subject-card {
  position: relative;
  overflow: hidden;
  cursor: pointer;
}

.subject-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--card-accent, var(--brand-500));
  opacity: 0;
  transition: opacity var(--t-base) var(--ease-out);
}

.subject-card:hover::before { opacity: 1; }

.subject-card .subject-icon {
  width: 48px; height: 48px;
  border-radius: var(--r-lg);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.25rem;
  background: color-mix(in srgb, var(--card-accent, var(--brand-500)) 15%, transparent);
  color: var(--card-accent, var(--brand-500));
  transition: transform var(--t-base) var(--ease-out);
}

.subject-card:hover .subject-icon { transform: scale(1.1); }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: var(--sp-2);
  font-weight: 700; border-radius: var(--r-xl);
  transition: all var(--t-base) var(--ease-out);
  white-space: nowrap;
}

.btn-primary {
  background: var(--brand-600);
  color: #fff;
  padding: var(--sp-4) var(--sp-8);
  font-size: var(--fs-lg);
  box-shadow: 0 0 30px var(--brand-glow);
}
.btn-primary:hover { background: var(--brand-500); transform: translateY(-1px); }

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text-primary);
  padding: var(--sp-3) var(--sp-6);
  border: 1px solid var(--border-default);
}
.btn-secondary:hover { border-color: var(--brand-500); background: var(--bg-glass-hover); }

.btn-sm {
  padding: var(--sp-2) var(--sp-4);
  font-size: var(--fs-sm);
  border-radius: var(--r-md);
}

.btn-danger {
  background: rgba(239, 68, 68, 0.1);
  color: var(--error);
  border: 1px solid rgba(239, 68, 68, 0.3);
  padding: var(--sp-4);
  border-radius: var(--r-xl);
}
.btn-danger:hover { border-color: var(--error); background: rgba(239, 68, 68, 0.2); }

.btn-module {
  width: 100%;
  padding: var(--sp-2) var(--sp-4);
  font-size: var(--fs-sm);
  font-weight: 700;
  border-radius: var(--r-md);
  color: #fff;
  background: var(--card-accent, var(--brand-600));
  opacity: 0.85;
  transition: opacity var(--t-fast);
}
.btn-module:hover { opacity: 1; }

/* Progress Bar */
.progress-track {
  width: 100%;
  height: 6px;
  background: var(--bg-elevated);
  border-radius: var(--r-full);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  border-radius: var(--r-full);
  background: var(--card-accent, var(--brand-500));
  transition: width var(--t-slow) var(--ease-out);
}

.progress-track-lg { height: 10px; }

/* Progress Ring (SVG) */
.progress-ring { transform: rotate(-90deg); }
.progress-ring-bg { fill: none; stroke: var(--bg-elevated); }
.progress-ring-fill {
  fill: none;
  stroke: var(--card-accent, var(--brand-500));
  stroke-linecap: round;
  transition: stroke-dashoffset 0.6s var(--ease-out);
}

/* Nav Pill */
.nav-pill {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  width: 4rem; padding: var(--sp-2);
  border-radius: var(--r-lg);
  color: var(--text-muted);
  font-size: var(--fs-xs);
  font-weight: 700;
  transition: all var(--t-fast);
}
.nav-pill.active, .nav-pill:hover {
  color: #fff;
  background: rgba(255,255,255,0.08);
}
.nav-pill i { font-size: 1.25rem; }

/* Tab Chip */
.tab-chip {
  padding: var(--sp-2) var(--sp-5);
  border-radius: var(--r-full);
  background: var(--bg-glass);
  border: 1px solid var(--border-subtle);
  font-size: var(--fs-sm);
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
  transition: all var(--t-fast);
  cursor: pointer;
}
.tab-chip.active, .tab-chip:hover {
  background: rgba(139, 92, 246, 0.15);
  border-color: var(--brand-500);
  color: #fff;
}

/* Badge */
.badge {
  display: inline-flex; align-items: center; gap: var(--sp-1);
  padding: 2px var(--sp-3);
  border-radius: var(--r-full);
  font-size: var(--fs-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.badge-brand {
  background: rgba(139, 92, 246, 0.15);
  color: var(--brand-400);
  border: 1px solid rgba(139, 92, 246, 0.25);
}
.badge-xp {
  background: rgba(245, 158, 11, 0.12);
  color: var(--warning);
  border: 1px solid rgba(245, 158, 11, 0.25);
}

/* Input */
.input {
  width: 100%;
  background: rgba(15, 23, 42, 0.6);
  border: 1px solid var(--border-default);
  color: var(--text-primary);
  border-radius: var(--r-xl);
  padding: var(--sp-3) var(--sp-4);
  font-size: var(--fs-base);
  outline: none;
  transition: border-color var(--t-fast);
}
.input:focus { border-color: var(--brand-500); }
.input.input-error { border-color: var(--error); }

/* Grade Selector Button */
.grade-btn {
  padding: var(--sp-6);
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-default);
  border-radius: var(--r-xl);
  cursor: pointer;
  transition: all var(--t-base) var(--ease-out);
}
.grade-btn:hover, .grade-btn.selected {
  border-color: var(--brand-500);
  background: rgba(139, 92, 246, 0.1);
}

/* Topic Accordion */
.topic-group { margin-bottom: var(--sp-4); }

.topic-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: var(--sp-3) var(--sp-4);
  background: var(--bg-glass);
  border: 1px solid var(--border-subtle);
  border-radius: var(--r-lg);
  cursor: pointer;
  transition: all var(--t-fast);
  user-select: none;
}
.topic-header:hover { border-color: var(--border-default); background: var(--bg-glass-hover); }
.topic-header .chevron {
  transition: transform var(--t-base) var(--ease-out);
  color: var(--text-muted);
}
.topic-group.open .topic-header .chevron { transform: rotate(180deg); }
.topic-group.open .topic-header { border-color: var(--border-strong); }

.topic-modules {
  display: none;
  padding: var(--sp-3) 0 0 0;
}
.topic-group.open .topic-modules { display: grid; gap: var(--sp-3); }

/* Stat Card */
.stat-card {
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-default);
  border-radius: var(--r-xl);
  padding: var(--sp-5);
}

/* Avatar */
.avatar {
  border-radius: var(--r-full);
  overflow: hidden;
  display: flex; align-items: center; justify-content: center;
}
.avatar img { width: 100%; height: 100%; object-fit: cover; }
.avatar-sm { width: 32px; height: 32px; }
.avatar-lg { width: 96px; height: 96px; border: 2px solid var(--brand-500); }

/* Breadcrumb */
.breadcrumb {
  display: flex; align-items: center; gap: var(--sp-2);
  font-size: var(--fs-sm);
  color: var(--text-muted);
  margin-bottom: var(--sp-4);
}
.breadcrumb a { color: var(--text-secondary); transition: color var(--t-fast); }
.breadcrumb a:hover { color: var(--brand-400); }
.breadcrumb .sep { opacity: 0.4; }
.breadcrumb .current { color: var(--text-primary); font-weight: 600; }

/* --- Backgrounds --- */
.mesh-bg {
  background-image:
    radial-gradient(ellipse 80% 60% at 10% 0%, rgba(139,92,246,0.12) 0%, transparent 60%),
    radial-gradient(ellipse 60% 50% at 90% 10%, rgba(56,189,248,0.08) 0%, transparent 50%),
    radial-gradient(ellipse 50% 40% at 50% 100%, rgba(16,185,129,0.06) 0%, transparent 50%);
}

/* --- Utility --- */
.view-hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0,0,0,0); border: 0; }
.truncate { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.pointer { cursor: pointer; }
.no-wrap { white-space: nowrap; }
.rounded-full { border-radius: var(--r-full); }

/* --- Animations --- */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes slideDown {
  from { opacity: 0; transform: translateY(-16px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.92); }
  to { opacity: 1; transform: scale(1); }
}
@keyframes pulse-glow {
  0%, 100% { box-shadow: 0 0 20px var(--brand-glow); }
  50% { box-shadow: 0 0 40px var(--brand-glow); }
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}
@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

.animate-fade-in { animation: fadeIn 0.35s var(--ease-out) forwards; }
.animate-slide-up { animation: slideUp 0.45s var(--ease-out) forwards; }
.animate-slide-down { animation: slideDown 0.4s var(--ease-out) forwards; }
.animate-scale-in { animation: scaleIn 0.35s var(--ease-out) forwards; }
.animate-float { animation: float 3s ease-in-out infinite; }
.animate-pulse-glow { animation: pulse-glow 2s ease-in-out infinite; }

/* Stagger children */
.stagger > *:nth-child(1) { animation-delay: 0ms; }
.stagger > *:nth-child(2) { animation-delay: 60ms; }
.stagger > *:nth-child(3) { animation-delay: 120ms; }
.stagger > *:nth-child(4) { animation-delay: 180ms; }
.stagger > *:nth-child(5) { animation-delay: 240ms; }
.stagger > *:nth-child(6) { animation-delay: 300ms; }
.stagger > * { opacity: 0; animation-fill-mode: forwards; }

/* --- Math Block (Lessons) --- */
.math-block {
  background: rgba(15, 23, 42, 0.8);
  border: 1px solid rgba(139, 92, 246, 0.25);
  border-left: 4px solid var(--brand-500);
  padding: var(--sp-4);
  border-radius: var(--r-md);
  font-family: 'Fira Code', 'Cascadia Code', monospace;
  font-size: var(--fs-lg);
  margin: var(--sp-4) 0;
  color: #e2e8f0;
}

/* --- Responsive --- */
@media (max-width: 639px) {
  .grid-cols-2 { grid-template-columns: 1fr; }
  .grid-cols-3 { grid-template-columns: 1fr; }
  .text-4xl { font-size: var(--fs-3xl); }
  .hide-mobile { display: none; }
}

@media (min-width: 640px) and (max-width: 1023px) {
  .grid-cols-3 { grid-template-columns: repeat(2, 1fr); }
}