/* Reset and Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #0a0a0a 0%, #1a1a1a 100%);
  color: #e0e0e0;
  line-height: 1.6;
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Header Styles */
.header {
  background: rgba(0, 0, 0, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 2px solid #00bcd4;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
}
.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
}
.nav-brand h1 {
  color: #00bcd4;
  font-size: 1.8rem;
  font-weight: bold;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 2rem;
}

.nav-link {
  color: #e0e0e0;
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 5px;
  transition: all 0.3s ease;
}

.nav-link:hover,
.nav-link.active {
  background: #00bcd4;
  color: #000;
}

/* Hero Section */
.hero {
  padding: 4rem 2rem;
  text-align: center;
  background: radial-gradient(circle at center, rgba(0, 188, 212, 0.1) 0%, transparent 70%);
}

.hero-title {
  font-size: 3.5rem;
  margin-bottom: 1rem;
  background: linear-gradient(45deg, #00bcd4, #4dd0e1);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.3rem;
  margin-bottom: 2rem;
  color: #b0b0b0;
}

/* Image Placeholders */
.image-placeholder {
  text-align: center;
  color: #00bcd4;
  font-weight: bold;
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.image-border {
  background: linear-gradient(135deg, #2a2a2a, #1a1a1a);
  border: 2px dashed #00bcd4;
  border-radius: 10px;
}
.image-placeholder.small {
  min-height: 120px;
  padding: 1rem;
  font-size: 0.9rem;
}

/* Topics Section */
.topics {
  padding: 4rem 2rem;
}

.section-title {
  text-align: center;
  font-size: 2.5rem;
  margin-bottom: 3rem;
  color: #00bcd4;
}

.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.topic-card {
  background: linear-gradient(135deg, #2a2a2a, #1a1a1a);
  border: 1px solid #333;
  border-radius: 15px;
  padding: 2rem;
  text-align: center;
  transition: all 0.3s ease;
  box-shadow: 0 4px 20px rgba(0, 188, 212, 0.1);
}

.topic-card:hover {
  transform: translateY(-5px);
  border-color: #00bcd4;
  box-shadow: 0 8px 30px rgba(0, 188, 212, 0.2);
}

.topic-icon {
  color: #00bcd4;
  font-size: 3rem;
  margin-bottom: 1rem;
}

.topic-card h3 {
  color: #00bcd4;
  font-size: 1.5rem;
  margin-bottom: 1rem;
}

.topic-card p {
  color: #b0b0b0;
  margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.8rem 2rem;
  text-decoration: none;
  border-radius: 25px;
  font-weight: bold;
  transition: all 0.3s ease;
  border: none;
  cursor: pointer;
  font-size: 1rem;
}

.btn-primary {
  background: linear-gradient(45deg, #00bcd4, #4dd0e1);
  color: #000;
}

.btn-primary:hover {
  background: linear-gradient(45deg, #4dd0e1, #00bcd4);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0, 188, 212, 0.3);
}

.btn-secondary {
  background: transparent;
  color: #00bcd4;
  border: 2px solid #00bcd4;
}

.btn-secondary:hover {
  background: #00bcd4;
  color: #000;
}

/* About Section */
.about {
  padding: 4rem 2rem;
  background: rgba(0, 0, 0, 0.3);
}

.about-content {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
}

.about-text p {
  margin-bottom: 1rem;
  font-size: 1.1rem;
  color: #b0b0b0;
}

/* Quiz Styles */
.quiz-container {
  background: linear-gradient(135deg, #2a2a2a, #1a1a1a);
  border-radius: 15px;
  padding: 2rem;
  margin: 2rem 0;
  border: 1px solid #333;
}

.question {
  margin-bottom: 2rem;
}

.question h3 {
  color: #00bcd4;
  margin-bottom: 1rem;
  font-size: 1.2rem;
}

.options {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.option {
  background: #333;
  border: 1px solid #555;
  border-radius: 8px;
  padding: 0.8rem;
  cursor: pointer;
  transition: all 0.3s ease;
}

.option:hover {
  background: #444;
  border-color: #00bcd4;
}

.option.selected {
  background: #00bcd4;
  color: #000;
  border-color: #4dd0e1;
}

.option.correct {
  background: #4caf50;
  color: white;
}

.option.incorrect {
  background: #f44336;
  color: white;
}

.quiz-score {
  text-align: center;
  font-size: 1.5rem;
  margin: 2rem 0;
  padding: 1rem;
  background: linear-gradient(135deg, #2a2a2a, #1a1a1a);
  border-radius: 10px;
  border: 2px solid #00bcd4;
}

.score-excellent {
  color: #4caf50;
}
.score-good {
  color: #00bcd4;
}
.score-fair {
  color: #ff9800;
}
.score-poor {
  color: #f44336;
}

/* Content Styles */
.content {
  padding: 2rem;
  max-width: 1000px;
  margin: 0 auto;
}

.content h1 {
  color: #00bcd4;
  font-size: 2.5rem;
  margin-bottom: 1rem;
  text-align: center;
}

.content h2 {
  color: #4dd0e1;
  font-size: 1.8rem;
  margin: 2rem 0 1rem 0;
  border-bottom: 2px solid #00bcd4;
  padding-bottom: 0.5rem;
}

.content h3 {
  color: #00bcd4;
  font-size: 1.3rem;
  margin: 1.5rem 0 0.5rem 0;
}

.content p {
  margin-bottom: 1rem;
  color: #e0e0e0;
  font-size: 1.1rem;
}

.content ul {
  margin: 1rem 0;
  padding-left: 2rem;
}

.content li {
  margin-bottom: 0.5rem;
  color: #b0b0b0;
}

.highlight {
  background: rgba(0, 188, 212, 0.2);
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  color: #4dd0e1;
}

/* Footer */
.footer {
  background: #000;
  text-align: center;
  padding: 2rem;
  border-top: 2px solid #00bcd4;
  margin-top: 4rem;
}

/* Responsive Design */
@media (max-width: 768px) {
  .nav {
    flex-direction: column;
    gap: 1rem;
  }

  .nav-links {
    gap: 1rem;
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .topics-grid {
    grid-template-columns: 1fr;
  }

  .about-content {
    grid-template-columns: 1fr;
  }

  .container {
    padding: 0 15px;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 2rem;
  }

  .hero-subtitle {
    font-size: 1.1rem;
  }

  .topic-card {
    padding: 1.5rem;
  }
}