/* ==========================================================================
   PowerUpEnglish - Stylesheet
   Modern, accessible and responsive styles for GitHub Pages / Jekyll
   ========================================================================== */

:root {
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #eef2ff;
  --primary-dark: #3730a3;

  /* Category colors */
  --cat-vocab: #059669;
  --cat-vocab-bg: #ecfdf5;
  --cat-vocab-border: #a7f3d0;

  --cat-grammar: #2563eb;
  --cat-grammar-bg: #eff6ff;
  --cat-grammar-border: #bfdbfe;

  --cat-use: #7c3aed;
  --cat-use-bg: #f5f3ff;
  --cat-use-border: #ddd6fe;

  --cat-exercises: #d97706;
  --cat-exercises-bg: #fffbeb;
  --cat-exercises-border: #fde68a;

  /* Neutrals */
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-sidebar: #ffffff;
  --bg-header: #ffffff;
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --border-color: #e2e8f0;
  --border-subtle: #f1f5f9;

  /* Layout dimensions */
  --header-height: 70px;
  --sidebar-width: 280px;
  --max-content-width: 1280px;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

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

html {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text-main);
  background-color: var(--bg-page);
  line-height: 1.6;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--primary-hover);
}

img, svg {
  vertical-align: middle;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

/* ==========================================================================
   Language Swap Engine (EN / ES)
   Only elements with .lang-en and .lang-es are affected
   ========================================================================== */
html[data-lang="en"] .lang-es,
body.lang-en .lang-es {
  display: none !important;
}

html[data-lang="es"] .lang-en,
body.lang-es .lang-en {
  display: none !important;
}

/* ==========================================================================
   Header & Navigation Bar
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-height);
  background-color: var(--bg-header);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
}

.header-container {
  max-width: 1600px;
  height: 100%;
  margin: 0 auto;
  padding: 0 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.sidebar-toggle-btn {
  display: none;
  padding: 0.5rem;
  border-radius: 8px;
  color: var(--text-muted);
  background-color: var(--border-subtle);
  font-size: 1.25rem;
  line-height: 1;
}

.sidebar-toggle-btn:hover {
  background-color: var(--border-color);
  color: var(--text-main);
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 800;
  font-size: 1.35rem;
  color: var(--text-main);
  letter-spacing: -0.02em;
}

.brand-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, #4f46e5 0%, #06b6d4 100%);
  color: #fff;
  border-radius: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 4px rgba(79, 70, 229, 0.3);
}

.brand-logo span.accent {
  color: var(--primary);
}

.header-right {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

/* Level Menu in Top Bar */
.level-nav-list {
  display: flex;
  align-items: center;
  list-style: none;
  gap: 0.35rem;
}

.level-nav-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.4rem 0.8rem;
  border-radius: 6px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-muted);
  border: 1px solid transparent;
  transition: all var(--transition-fast);
}

.level-nav-link:hover {
  background-color: var(--primary-light);
  color: var(--primary);
}

.level-nav-link.active {
  background-color: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
}

/* Language Swap Button in Header */
.lang-swap-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.9rem;
  background: var(--bg-card);
  border: 1.5px solid var(--border-color);
  border-radius: 9999px;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-main);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}

.lang-swap-btn:hover {
  border-color: var(--primary);
  background-color: var(--primary-light);
  color: var(--primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.lang-flag {
  font-size: 1.1rem;
}

/* ==========================================================================
   Main Layout (Sidebar + Content)
   ========================================================================== */
.site-body {
  display: flex;
  flex: 1;
  max-width: 1600px;
  width: 100%;
  margin: 0 auto;
  position: relative;
}

/* Left Vertical Panel (Sidebar) */
.site-sidebar {
  width: var(--sidebar-width);
  flex-shrink: 0;
  background-color: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  height: calc(100vh - var(--header-height));
  position: sticky;
  top: var(--header-height);
  overflow-y: auto;
  padding: 1.5rem 1rem;
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-normal);
}

.sidebar-header {
  padding-bottom: 1rem;
  margin-bottom: 1rem;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-level-badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  background-color: var(--primary-light);
  color: var(--primary);
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.sidebar-title {
  font-size: 1.15rem;
  font-weight: 750;
  color: var(--text-main);
}

.sidebar-level-select {
  width: 100%;
  margin-top: 0.75rem;
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background-color: var(--bg-page);
  color: var(--text-main);
  font-weight: 600;
  font-size: 0.875rem;
  cursor: pointer;
  outline: none;
}

.sidebar-level-select:focus {
  border-color: var(--primary);
}

/* Sidebar Menu Items */
.sidebar-nav-group {
  margin-bottom: 1.5rem;
}

.sidebar-nav-title {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-light);
  margin-bottom: 0.5rem;
  padding: 0 0.5rem;
}

.sidebar-menu-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.sidebar-menu-item a {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.6rem 0.75rem;
  border-radius: 8px;
  color: var(--text-main);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
}

.sidebar-menu-item a:hover {
  background-color: var(--border-subtle);
  color: var(--primary);
  transform: translateX(2px);
}

.sidebar-menu-item.active a {
  background-color: var(--primary-light);
  color: var(--primary-dark);
  font-weight: 700;
  border-color: var(--primary-light);
}

/* Category Icons & Tags */
.cat-icon-wrap {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: transform var(--transition-fast);
}

.sidebar-menu-item a:hover .cat-icon-wrap {
  transform: scale(1.1);
}

.cat-vocabulary .cat-icon-wrap {
  background-color: var(--cat-vocab-bg);
  color: var(--cat-vocab);
}

.cat-grammar .cat-icon-wrap {
  background-color: var(--cat-grammar-bg);
  color: var(--cat-grammar);
}

.cat-use-of-english .cat-icon-wrap {
  background-color: var(--cat-use-bg);
  color: var(--cat-use);
}

.cat-exercises .cat-icon-wrap {
  background-color: var(--cat-exercises-bg);
  color: var(--cat-exercises);
}

.sidebar-link-text {
  flex: 1;
  line-height: 1.3;
}

.cat-tag-pill {
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  letter-spacing: 0.03em;
}

.cat-tag-vocabulary {
  background-color: var(--cat-vocab-bg);
  color: var(--cat-vocab);
}

.cat-tag-grammar {
  background-color: var(--cat-grammar-bg);
  color: var(--cat-grammar);
}

.cat-tag-use-of-english {
  background-color: var(--cat-use-bg);
  color: var(--cat-use);
}

.cat-tag-exercises {
  background-color: var(--cat-exercises-bg);
  color: var(--cat-exercises);
}

/* ==========================================================================
   Main Content Area
   ========================================================================== */
.site-main {
  flex: 1;
  padding: 2rem 1.5rem;
  max-width: var(--max-content-width);
  margin: 0 auto;
  width: 100%;
}

/* Breadcrumb */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.breadcrumb-separator {
  color: var(--text-light);
}

/* Page Header */
.page-header-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 2rem;
  margin-bottom: 2rem;
  box-shadow: var(--shadow-sm);
}

.page-header-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}

.page-title {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.025em;
  color: var(--text-main);
  line-height: 1.25;
}

.page-lead {
  font-size: 1.15rem;
  color: var(--text-muted);
  margin-top: 0.75rem;
  line-height: 1.6;
}

/* Content Box Cards */
.content-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 2rem;
  margin-bottom: 2rem;
  box-shadow: var(--shadow-sm);
}

.content-card h2 {
  font-size: 1.4rem;
  font-weight: 750;
  margin-bottom: 1rem;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.content-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-top: 1.5rem;
  margin-bottom: 0.75rem;
  color: var(--text-main);
}

.content-card p {
  margin-bottom: 1rem;
  font-size: 1.05rem;
  line-height: 1.7;
}

/* Bilingual Notice Box */
.bilingual-notice {
  background-color: var(--primary-light);
  border-left: 4px solid var(--primary);
  border-radius: 0 8px 8px 0;
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
  font-size: 0.95rem;
  color: var(--primary-dark);
}

/* Example tables & list for dual languages (non-swap example) */
.dual-lang-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.dual-lang-table th {
  background-color: var(--border-subtle);
  color: var(--text-main);
  text-align: left;
  padding: 0.85rem 1rem;
  font-weight: 700;
  border-bottom: 2px solid var(--border-color);
}

.dual-lang-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-color);
  background-color: var(--bg-card);
}

.dual-lang-table tr:hover td {
  background-color: var(--primary-light);
}

/* Audio Pronunciation Buttons */
.audio-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background-color: var(--primary-light);
  color: var(--primary);
  border: 1px solid var(--border-color);
  margin-left: 0.45rem;
  vertical-align: middle;
  cursor: pointer;
  transition: all var(--transition-fast);
  padding: 0;
  flex-shrink: 0;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

.audio-btn:hover {
  background-color: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
  transform: scale(1.15);
  box-shadow: 0 2px 6px rgba(79, 70, 229, 0.35);
}

.audio-btn:active {
  transform: scale(0.92);
}

.audio-btn.is-playing {
  background-color: #10b981;
  color: #ffffff;
  border-color: #059669;
  animation: audioPulse 0.8s infinite alternate ease-in-out;
}

@keyframes audioPulse {
  0% { transform: scale(1); box-shadow: 0 0 0 0 rgba(16, 185, 129, 0.6); }
  100% { transform: scale(1.18); box-shadow: 0 0 0 6px rgba(16, 185, 129, 0); }
}

.audio-btn svg {
  width: 13px;
  height: 13px;
  pointer-events: none;
}

/* Pagination / Next & Prev Links */
.page-navigation {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
}

.nav-button {
  display: inline-flex;
  flex-direction: column;
  padding: 1rem 1.25rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  min-width: 180px;
  transition: all var(--transition-fast);
  box-shadow: var(--shadow-sm);
}

.nav-button:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.nav-button-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  color: var(--text-light);
  margin-bottom: 0.25rem;
}

.nav-button-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-main);
}

.nav-button.next {
  text-align: right;
  margin-left: auto;
}

/* ==========================================================================
   Home Page Hero & Grid Styles
   ========================================================================== */
.hero-section {
  background: linear-gradient(135deg, #4f46e5 0%, #3730a3 100%);
  color: #ffffff;
  border-radius: 16px;
  padding: 3.5rem 2.5rem;
  margin-bottom: 2.5rem;
  box-shadow: var(--shadow-lg);
  position: relative;
  overflow: hidden;
}

.hero-section::after {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(255,255,255,0.15) 0%, rgba(255,255,255,0) 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero-title {
  font-size: 2.5rem;
  font-weight: 850;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  line-height: 1.2;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: #e0e7ff;
  max-width: 650px;
  line-height: 1.6;
  margin-bottom: 1.75rem;
}

.hero-badge-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: rgba(255, 255, 255, 0.15);
  backdrop-filter: blur(8px);
  padding: 0.4rem 0.85rem;
  border-radius: 9999px;
  font-size: 0.85rem;
  font-weight: 600;
}

/* Level Grid on Index */
.levels-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-bottom: 3rem;
}

.level-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 1.5rem;
  transition: all var(--transition-fast);
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-sm);
  position: relative;
}

.level-card:hover {
  border-color: var(--primary);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.level-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}

.level-pill {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--primary);
  background: var(--primary-light);
  padding: 0.25rem 0.65rem;
  border-radius: 6px;
}

.level-card-title {
  font-size: 1.25rem;
  font-weight: 750;
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

.level-card-desc {
  font-size: 0.925rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 1.25rem;
  flex: 1;
}

.level-card-topics-list {
  list-style: none;
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.75rem;
  margin-bottom: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.level-card-topics-list li a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.875rem;
  color: var(--text-main);
  padding: 0.25rem 0;
}

.level-card-topics-list li a:hover {
  color: var(--primary);
}

.level-card-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1rem;
  background: var(--primary-light);
  color: var(--primary-dark);
  font-weight: 700;
  font-size: 0.9rem;
  border-radius: 8px;
  text-align: center;
  transition: all var(--transition-fast);
}

.level-card-btn:hover {
  background: var(--primary);
  color: #ffffff;
}

/* Pillars Section */
.pillars-section {
  margin-bottom: 3rem;
}

.section-title {
  font-size: 1.6rem;
  font-weight: 800;
  margin-bottom: 1.5rem;
  color: var(--text-main);
}

.pillars-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
}

.pillar-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.pillar-card-icon {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1rem;
  font-size: 1.25rem;
}

.pillar-vocab .pillar-card-icon {
  background: var(--cat-vocab-bg);
  color: var(--cat-vocab);
}

.pillar-grammar .pillar-card-icon {
  background: var(--cat-grammar-bg);
  color: var(--cat-grammar);
}

.pillar-use .pillar-card-icon {
  background: var(--cat-use-bg);
  color: var(--cat-use);
}

.pillar-exercises .pillar-card-icon {
  background: var(--cat-exercises-bg);
  color: var(--cat-exercises);
}

.pillar-card h3 {
  font-size: 1.1rem;
  font-weight: 750;
  margin-bottom: 0.5rem;
}

.pillar-card p {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.5;
}

/* Floating Language Swap Button */
.floating-swap-pill {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 60;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 1.15rem;
  background-color: var(--text-main);
  color: #ffffff;
  border-radius: 9999px;
  font-size: 0.875rem;
  font-weight: 700;
  box-shadow: var(--shadow-xl);
  border: 2px solid rgba(255, 255, 255, 0.2);
  transition: all var(--transition-fast);
}

.floating-swap-pill:hover {
  transform: translateY(-2px) scale(1.03);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.25);
  background-color: var(--primary);
}

/* ==========================================================================
   Footer
   ========================================================================== */
.site-footer {
  background-color: #0f172a;
  color: #94a3b8;
  border-top: 1px solid #1e293b;
  padding: 2.5rem 1rem;
  margin-top: auto;
}

.footer-container {
  max-width: 1600px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.footer-brand {
  font-size: 1.1rem;
  font-weight: 700;
  color: #ffffff;
}

.footer-links {
  display: flex;
  gap: 1.25rem;
  list-style: none;
}

.footer-links a {
  color: #94a3b8;
  font-size: 0.875rem;
}

.footer-links a:hover {
  color: #ffffff;
}

/* ==========================================================================
   Responsive Breakpoints
   ========================================================================== */
@media (max-width: 1024px) {
  :root {
    --sidebar-width: 280px;
  }
  .site-main {
    padding: 2rem 1.5rem;
  }
}

@media (max-width: 768px) {
  .sidebar-toggle-btn {
    display: inline-flex;
  }

  .level-nav-list {
    display: none; /* Accessible in sidebar and drawer */
  }

  .site-sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    bottom: 0;
    z-index: 40;
    transform: translateX(-100%);
    box-shadow: var(--shadow-xl);
  }

  .site-sidebar.is-open {
    transform: translateX(0);
  }

  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.4);
    z-index: 35;
    backdrop-filter: blur(2px);
  }

  .sidebar-backdrop.is-open {
    display: block;
  }

  .site-main {
    padding: 1.5rem 1rem;
  }

  .hero-section {
    padding: 2rem 1.5rem;
  }

  .hero-title {
    font-size: 1.85rem;
  }

  .page-title {
    font-size: 1.5rem;
  }

  .page-navigation {
    flex-direction: column;
  }

  .nav-button.next {
    margin-left: 0;
  }
}