:root {
  --bg-dark: #070d1e;
  --panel-bg: rgba(15, 23, 42, 0.85);
  --card-bg: rgba(22, 34, 66, 0.7);
  --border-color: rgba(56, 189, 248, 0.2);
  --accent-cyan: #38bdf8;
  --accent-blue: #3b82f6;
  --accent-green: #10b981;
  --accent-orange: #f59e0b;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Vazirmatn', sans-serif;
}

body {
  background: var(--bg-dark);
  color: var(--text-main);
  min-height: 100vh;
  line-height: 1.8;
}

.screen {
  display: none;
}

.screen.active {
  display: block;
}

/* Auth */
#auth-screen {
  display: none;
  min-height: 100vh;
  place-items: center;
  padding: 20px;
}

#auth-screen.active {
  display: grid;
}

.auth-card {
  background: var(--panel-bg);
  border: 1px solid var(--border-color);
  padding: 40px 30px;
  border-radius: 20px;
  max-width: 440px;
  width: 100%;
  text-align: center;
  backdrop-filter: blur(15px);
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.7);
}

.badge {
  display: inline-block;
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent-cyan);
  padding: 4px 14px;
  border-radius: 30px;
  font-size: 0.85rem;
  font-weight: 700;
  margin-bottom: 15px;
}

.auth-card h2 {
  margin-bottom: 10px;
  font-weight: 900;
}

.auth-card p {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 25px;
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

input[type="password"] {
  background: rgba(7, 13, 30, 0.9);
  border: 1px solid var(--border-color);
  padding: 14px 18px;
  border-radius: 12px;
  color: #fff;
  font-size: 1rem;
  text-align: center;
  outline: none;
  transition: 0.2s;
}

input[type="password"]:focus {
  border-color: var(--accent-cyan);
  box-shadow: 0 0 10px rgba(56, 189, 248, 0.3);
}

button {
  cursor: pointer;
  border: none;
  border-radius: 12px;
  padding: 13px 20px;
  font-size: 0.95rem;
  font-weight: 700;
  transition: 0.2s;
}

#btn-login,
.btn-primary {
  background: linear-gradient(135deg, var(--accent-blue), #1d4ed8);
  color: #fff;
}

#btn-login:hover,
.btn-primary:hover {
  filter: brightness(1.15);
}

.error-msg {
  color: #f87171;
  font-size: 0.85rem;
  margin-top: 12px;
  min-height: 20px;
}

/* Navbar */
.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 35px;
  background: rgba(7, 13, 30, 0.95);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 50;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.logo-icon {
  font-size: 2rem;
}

.nav-brand h3 {
  font-size: 1.1rem;
  font-weight: 800;
}

.nav-brand small {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 15px;
}

.student-badge {
  background: #1e293b;
  padding: 6px 14px;
  border-radius: 8px;
  font-size: 0.85rem;
  border: 1px solid #334155;
}

.btn-outline {
  background: transparent;
  border: 1px solid #475569;
  color: var(--text-muted);
}

.btn-outline:hover {
  background: #334155;
  color: #fff;
}

/* Layout */
.layout {
  display: grid;
  grid-template-columns: 310px 1fr;
  min-height: calc(100vh - 78px);
}

.sidebar {
  background: rgba(11, 19, 43, 0.7);
  border-left: 1px solid var(--border-color);
  padding: 30px 20px;
}

.sidebar h4 {
  margin-bottom: 18px;
  font-size: 0.95rem;
  color: var(--accent-cyan);
  font-weight: 800;
}

.lesson-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.lesson-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px;
  border-radius: 14px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: 0.2s;
}

.lesson-item:hover {
  background: rgba(56, 189, 248, 0.08);
}

.lesson-item.active {
  background: rgba(37, 99, 235, 0.25);
  border-color: var(--accent-blue);
}

.lesson-item .num {
  background: #1e293b;
  min-width: 28px;
  height: 28px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: 0.85rem;
  margin-top: 2px;
}

/* استایل ظریف مخصوص نشان جلسه صفر */
.lesson-item[data-lesson="0"] .num {
  background: rgba(16, 185, 129, 0.18);
  border: 1px solid rgba(16, 185, 129, 0.45);
  color: #a7f3d0;
}

.lesson-item[data-lesson="0"].active .num {
  background: var(--accent-green);
  border-color: var(--accent-green);
  color: #062d25;
}

.lesson-item strong {
  display: block;
  font-size: 0.9rem;
  line-height: 1.4;
}

.lesson-item small {
  color: var(--text-muted);
  font-size: 0.78rem;
  display: block;
  margin-top: 4px;
}

/* Main Content */
.content-area {
  padding: 35px 50px;
  max-width: 1050px;
}

.lesson-content {
  display: none;
}

.lesson-content.active {
  display: block;
}

.lesson-header {
  margin-bottom: 30px;
}

.lesson-header h1 {
  font-size: 1.8rem;
  font-weight: 900;
  margin: 12px 0;
  color: #fff;
  line-height: 1.4;
}

.subtitle {
  color: var(--accent-cyan);
  font-size: 1rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 18px;
  padding: 28px;
  margin-bottom: 30px;
  backdrop-filter: blur(10px);
}

.card h2 {
  font-size: 1.35rem;
  margin-bottom: 15px;
  color: #fff;
  font-weight: 800;
}

.card p {
  color: #cbd5e1;
  font-size: 0.96rem;
  margin-bottom: 12px;
}

.section-title-wrap {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 15px;
}

.part-badge {
  background: #3b82f6;
  color: #fff;
  padding: 2px 10px;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 800;
}

/* Compare Concept Box */
.concept-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
  margin: 18px 0;
}

.concept-box {
  padding: 18px;
  border-radius: 14px;
  border: 1px solid var(--border-color);
}

.concept-box.intuitive {
  background: rgba(56, 189, 248, 0.08);
}

.concept-box.scientific {
  background: rgba(16, 185, 129, 0.08);
}

.concept-box h4 {
  font-size: 0.95rem;
  margin-bottom: 8px;
}

.concept-box.intuitive h4 {
  color: var(--accent-cyan);
}

.concept-box.scientific h4 {
  color: var(--accent-green);
}

.concept-box p {
  font-size: 0.9rem;
  line-height: 1.7;
  margin-bottom: 0;
}

/* Tech Details Grid */
.market-tech-details {
  margin-top: 20px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 18px;
}

.market-tech-details h3 {
  font-size: 1.05rem;
  margin-bottom: 14px;
  color: var(--accent-orange);
}

.tech-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 15px;
}

.tech-card {
  background: rgba(11, 19, 41, 0.8);
  border: 1px solid var(--border-color);
  padding: 16px;
  border-radius: 12px;
}

.tech-card strong {
  display: block;
  color: var(--accent-cyan);
  margin-bottom: 6px;
  font-size: 0.9rem;
}

.tech-card p {
  font-size: 0.85rem;
  line-height: 1.6;
  margin-bottom: 0;
}

/* Storage Table */
.storage-compare-table {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-top: 12px;
}

.storage-row {
  display: grid;
  grid-template-columns: 140px 1.5fr 1.2fr 1.5fr;
  gap: 12px;
  background: rgba(11, 19, 41, 0.8);
  padding: 12px 16px;
  border-radius: 10px;
  font-size: 0.85rem;
  align-items: center;
}

.storage-row.header {
  background: rgba(30, 58, 138, 0.4);
  font-weight: 800;
  color: var(--accent-cyan);
}

.storage-row .type-name {
  font-weight: 700;
  color: #fff;
}

/* General Grids */
.compare-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-top: 15px;
}

.compare-box {
  padding: 20px;
  border-radius: 14px;
  background: rgba(11, 19, 41, 0.7);
  border: 1px solid var(--border-color);
}

.compare-box h3 {
  margin-bottom: 10px;
  font-size: 1.1rem;
}

.compare-box.hw h3 {
  color: var(--accent-cyan);
}

.compare-box.sw h3 {
  color: var(--accent-green);
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 15px;
}

.tag-list span {
  background: #1e293b;
  font-size: 0.8rem;
  padding: 4px 10px;
  border-radius: 6px;
  color: #cbd5e1;
}

/* Quiz Styles */
.quiz-card {
  border-color: rgba(59, 130, 246, 0.4);
  background: rgba(15, 23, 42, 0.95);
}

.quiz-badge {
  display: inline-block;
  background: rgba(245, 158, 11, 0.2);
  color: var(--accent-orange);
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 800;
  margin-bottom: 12px;
}

.quiz-desc {
  color: var(--text-muted);
  margin-bottom: 25px;
}

.quiz-q {
  background: rgba(11, 19, 41, 0.7);
  border: 1px solid var(--border-color);
  padding: 18px 20px;
  border-radius: 12px;
  margin-bottom: 16px;
  transition: 0.2s;
}

.quiz-q p {
  margin-bottom: 12px;
  font-size: 0.95rem;
  color: #fff;
}

.quiz-q label {
  display: block;
  padding: 8px 12px;
  margin-bottom: 6px;
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  color: #cbd5e1;
  background: rgba(255, 255, 255, 0.02);
  transition: 0.15s;
}

.quiz-q label:hover {
  background: rgba(56, 189, 248, 0.1);
  color: #fff;
}

.quiz-q input {
  margin-left: 10px;
}

.quiz-result {
  margin-top: 25px;
  padding: 20px;
  border-radius: 14px;
  font-size: 1.05rem;
  line-height: 1.8;
}

.quiz-result.success {
  background: rgba(16, 185, 129, 0.2);
  border: 1px solid var(--accent-green);
  color: #a7f3d0;
}

.quiz-result.warning {
  background: rgba(245, 158, 11, 0.2);
  border: 1px solid #f59e0b;
  color: #fde68a;
}

.hidden {
  display: none;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    border-left: none;
    border-bottom: 1px solid var(--border-color);
  }

  .concept-split,
  .compare-grid {
    grid-template-columns: 1fr;
  }

  .storage-row {
    grid-template-columns: 1fr;
    gap: 4px;
  }

  .storage-row.header {
    display: none;
  }

  .content-area {
    padding: 20px;
  }
}