:root {
  --primary: #0f766e;
  --primary-light: #14b8a6;
  --primary-bg: #f0fdfa;
  --text: #1e293b;
  --text-light: #64748b;
  --white: #ffffff;
  --border: #e2e8f0;
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
  --radius: 12px;
  --transition: all 0.3s ease;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }
html[dir="rtl"] body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; }

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  color: var(--text);
  background: var(--white);
  line-height: 1.6;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }

/* Header */
header {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.development-notice {
  background: var(--primary-bg);
  border-bottom: 1px solid var(--border);
  border-left: 4px solid var(--primary);
}

.development-notice .container {
  padding-top: 12px;
  padding-bottom: 12px;
}

.development-notice p {
  margin: 0;
  color: var(--text);
  font-size: 0.95rem;
}

.development-notice strong {
  color: var(--primary);
}

html[dir="rtl"] .development-notice {
  border-left: 0;
  border-right: 4px solid var(--primary);
}

.logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  min-width: 0;
  line-height: 0;
}

.brand-logo {
  width: 250px;
  max-width: 100%;
  height: auto;
  display: block;
  object-fit: contain;
  filter: none;
}

nav { display: flex; align-items: center; gap: 8px; }

.nav-links {
  display: flex;
  gap: 4px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-light);
  font-weight: 500;
  padding: 8px 14px;
  border-radius: 8px;
  transition: var(--transition);
  font-size: 0.95rem;
}

.nav-links a:hover, .nav-links a.active {
  color: var(--primary);
  background: var(--primary-bg);
}

.lang-toggle {
  background: var(--primary-bg);
  border: 1px solid var(--primary-light);
  color: var(--primary);
  padding: 6px 14px;
  border-radius: 20px;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.85rem;
  transition: var(--transition);
  margin-left: 12px;
}

html[dir="rtl"] .lang-toggle { margin-left: 0; margin-right: 12px; }

.lang-toggle:hover { background: var(--primary); color: var(--white); }

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--primary);
}

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary-bg) 0%, var(--white) 100%);
  padding: 100px 0 80px;
  text-align: center;
}

.hero h1 {
  font-size: 3rem;
  color: var(--primary);
  margin-bottom: 16px;
  letter-spacing: -1px;
}

.hero-title-main,
.hero-title-sub {
  display: block;
}

.hero-title-sub {
  margin-top: 8px;
  font-size: 0.58em;
  line-height: 1.3;
  font-weight: 600;
}

.hero p {
  font-size: 1.25rem;
  color: var(--text-light);
  max-width: 600px;
  margin: 0 auto;
}

.homepage-shell {
  display: grid;
  grid-template-columns: 190px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
  max-width: 1480px;
  margin: 0 auto;
  padding: 0 24px;
}

.homepage-main {
  min-width: 0;
}

.home-sidebar {
  position: sticky;
  top: 96px;
  align-self: start;
  max-height: calc(100vh - 120px);
  overflow-y: auto;
  padding: 24px 0;
}

.home-sidebar-title {
  margin: 0 12px 12px;
  color: var(--text-light);
  font-size: 0.75rem;
  font-weight: 700;
  line-height: 1.4;
  text-transform: uppercase;
}

.home-sidebar nav {
  display: grid;
  gap: 4px;
}

.home-sidebar a {
  display: block;
  padding: 10px 12px;
  border-left: 3px solid transparent;
  border-radius: 0 4px 4px 0;
  color: var(--text-light);
  font-size: 0.9rem;
  font-weight: 500;
  line-height: 1.4;
  text-decoration: none;
  transition: var(--transition);
}

.home-sidebar a:hover,
.home-sidebar a:focus-visible {
  border-left-color: var(--primary);
  background: var(--primary-bg);
  color: var(--primary);
  outline: none;
}

html[dir="rtl"] .home-sidebar a {
  border-left: 0;
  border-right: 3px solid transparent;
  border-radius: 4px 0 0 4px;
}

html[dir="rtl"] .home-sidebar a:hover,
html[dir="rtl"] .home-sidebar a:focus-visible {
  border-right-color: var(--primary);
}

.homepage-main section[id] {
  scroll-margin-top: 96px;
}

/* Sections */
.section { padding: 80px 0; }
.section-alt { background: #f8fafc; }

.section-header {
  text-align: center;
  margin-bottom: 48px;
}

.section-header h2 {
  font-size: 2rem;
  color: var(--primary);
  margin-bottom: 12px;
}

.section-header p {
  color: var(--text-light);
  max-width: 600px;
  margin: 0 auto;
}

.project-copy {
  max-width: 920px;
  margin: 0 auto;
}

.project-copy p {
  font-size: 1.08rem;
  line-height: 1.85;
  color: var(--text);
  margin-bottom: 1.25rem;
}

.project-copy strong {
  color: var(--primary);
}

.project-copy em {
  color: var(--primary);
  font-style: italic;
}

/* Cards */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

.card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  transition: var(--transition);
  cursor: pointer;
  text-decoration: none;
  color: inherit;
  display: block;
}

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

.card-icon {
  width: 48px;
  height: 48px;
  background: var(--primary-bg);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 16px;
}

.card h3 {
  font-size: 1.15rem;
  margin-bottom: 8px;
  color: var(--text);
}

.card p {
  color: var(--text-light);
  font-size: 0.95rem;
}

/* Definition Box */
.definition-box {
  background: var(--primary-bg);
  border-left: 4px solid var(--primary);
  padding: 32px;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 24px 0;
}

html[dir="rtl"] .definition-box {
  border-left: none;
  border-right: 4px solid var(--primary);
  border-radius: var(--radius) 0 0 var(--radius);
}

.definition-box h3 {
  color: var(--primary);
  margin-bottom: 12px;
  font-size: 1.1rem;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.definition-box p {
  font-size: 1.1rem;
  line-height: 1.8;
  color: var(--text);
}

.definition-copy p + p {
  margin-top: 1rem;
}

.definition-copy strong,
.definition-copy em {
  color: var(--primary);
}

/* Calculator Embed */
.calculator-embed {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.calculator-embed iframe {
  width: 100%;
  min-height: 1600px;
  border: none;
  background: transparent;
  display: block;
  border-radius: 12px;
}

/* Video Module */
.video-module {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 40px;
  box-shadow: var(--shadow);
}

.video-player {
  background: #0f172a;
  aspect-ratio: 16/9;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  position: relative;
  transition: var(--transition);
}

.video-player:hover { background: #1e293b; }

.video-player .play-btn {
  width: 80px;
  height: 80px;
  background: rgba(255,255,255,0.9);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  color: var(--primary);
  transition: var(--transition);
}

.video-player:hover .play-btn {
  transform: scale(1.1);
  background: var(--white);
}

.video-info { padding: 24px 32px; }
.video-info h3 { margin-bottom: 8px; color: var(--text); }
.video-info p { color: var(--text-light); font-size: 0.95rem; }

/* Quiz */
.quiz-section {
  padding: 24px 32px 32px;
  border-top: 1px solid var(--border);
  background: #f8fafc;
}

.quiz-section h4 {
  margin-bottom: 16px;
  color: var(--primary);
  font-size: 1rem;
}

.quiz-question {
  margin-bottom: 20px;
}

.quiz-question p {
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--text);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.quiz-options button {
  text-align: left;
  padding: 12px 16px;
  border: 1px solid var(--border);
  background: var(--white);
  border-radius: 8px;
  cursor: pointer;
  transition: var(--transition);
  font-size: 0.95rem;
  color: var(--text);
}

.quiz-options button:hover {
  border-color: var(--primary-light);
  background: var(--primary-bg);
}

.quiz-options button.correct {
  background: #dcfce7;
  border-color: #22c55e;
  color: #15803d;
}

.quiz-options button.incorrect {
  background: #fee2e2;
  border-color: #ef4444;
  color: #b91c1c;
}

.quiz-feedback {
  margin-top: 8px;
  padding: 10px 14px;
  border-radius: 8px;
  font-size: 0.9rem;
  display: none;
}

.quiz-feedback.show { display: block; }
.quiz-feedback.correct { background: #dcfce7; color: #15803d; }
.quiz-feedback.incorrect { background: #fee2e2; color: #b91c1c; }

/* Resources List */
.resource-item {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 16px;
  transition: var(--transition);
}

.resource-item:hover {
  box-shadow: var(--shadow);
  border-color: var(--primary-light);
}

.resource-item h4 {
  color: var(--primary);
  margin-bottom: 6px;
  font-size: 1.1rem;
}

.resource-item p {
  color: var(--text-light);
  font-size: 0.95rem;
  margin-bottom: 8px;
}

.resource-tag {
  display: inline-block;
  background: var(--primary-bg);
  color: var(--primary);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
}

/* Contact */
.contact-form {
  max-width: 600px;
  margin: 0 auto;
  background: var(--white);
  padding: 40px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.form-group { margin-bottom: 20px; }
.form-group label {
  display: block;
  margin-bottom: 6px;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text);
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-family: inherit;
  font-size: 1rem;
  transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary-light);
  box-shadow: 0 0 0 3px rgba(20,184,166,0.1);
}

.btn {
  display: inline-block;
  padding: 12px 28px;
  background: var(--primary);
  color: var(--white);
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}

.btn:hover { background: var(--primary-light); transform: translateY(-1px); }
.btn-block { width: 100%; text-align: center; }

/* Footer */
footer {
  background: #0f172a;
  color: #94a3b8;
  padding: 40px 0;
  text-align: center;
  margin-top: 60px;
}

footer p { font-size: 0.9rem; }

/* Placeholder Content */
.placeholder-content {
  text-align: center;
  padding: 80px 40px;
  color: var(--text-light);
}

.placeholder-content .icon {
  font-size: 4rem;
  margin-bottom: 20px;
  opacity: 0.3;
}

.placeholder-content h2 {
  color: var(--text);
  margin-bottom: 12px;
}

/* Mobile */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 72px;
    left: 0;
    right: 0;
    background: var(--white);
    flex-direction: column;
    padding: 16px;
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
  }
  .nav-links.open { display: flex; }
  .mobile-menu-btn { display: block; }
  .hero h1 { font-size: 2rem; }
  .hero p { font-size: 1rem; }
  .section { padding: 60px 0; }
  .section-header h2 { font-size: 1.5rem; }
  .card-grid { grid-template-columns: 1fr; }
  .contact-form { padding: 24px; }
}

@media (max-width: 900px) {
  .homepage-shell {
    display: block;
    padding: 0;
  }

  .home-sidebar {
    top: 72px;
    z-index: 900;
    max-height: none;
    overflow-x: auto;
    overflow-y: hidden;
    padding: 0 16px;
    border-bottom: 1px solid var(--border);
    background: var(--white);
    scrollbar-width: thin;
  }

  .home-sidebar-title {
    display: none;
  }

  .home-sidebar nav {
    display: flex;
    width: max-content;
    min-width: 100%;
    gap: 4px;
  }

  .home-sidebar a {
    white-space: nowrap;
    border: 0;
    border-bottom: 3px solid transparent;
    border-radius: 0;
  }

  .home-sidebar a:hover,
  .home-sidebar a:focus-visible {
    border-left-color: transparent;
    border-bottom-color: var(--primary);
  }

  html[dir="rtl"] .home-sidebar a {
    border: 0;
    border-bottom: 3px solid transparent;
  }

  html[dir="rtl"] .home-sidebar a:hover,
  html[dir="rtl"] .home-sidebar a:focus-visible {
    border-right-color: transparent;
    border-bottom-color: var(--primary);
  }

  .homepage-main section[id] {
    scroll-margin-top: 132px;
  }
}

/* Utility */
.text-center { text-align: center; }
.mb-4 { margin-bottom: 16px; }
.mb-8 { margin-bottom: 32px; }
.mt-8 { margin-top: 32px; }