body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  margin: 0;
  padding: 0;
  background-color: #f5f7fa;
  color: #333;
}

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

header {
  background: linear-gradient(135deg, #6B73FF 0%, #000DFF 100%);
  color: white;
  padding: 2rem 0;
  text-align: center;
  border-radius: 0 0 20px 20px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

h1 {
  margin: 0;
  font-size: 2.5rem;
}

.subtitle {
  font-size: 1.2rem;
  opacity: 0.9;
  margin-top: 0.5rem;
}

nav {
  background-color: white;
  padding: 1rem;
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  margin: 20px 0;
}

nav ul {
  display: flex;
  justify-content: center;
  list-style: none;
  padding: 0;
  gap: 20px;
}

nav a {
  text-decoration: none;
  color: #4a6bff;
  font-weight: 600;
  padding: 0.5rem 1rem;
  border-radius: 5px;
  transition: all 0.3s ease;
}

nav a:hover {
  background-color: #eef2ff;
  color: #1a3dff;
}

.content {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 20px;
}

main {
  background-color: white;
  padding: 2rem;
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

aside {
  background-color: white;
  padding: 1.5rem;
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

h2 {
  color: #4a6bff;
  margin-top: 0;
}

.lesson-card {
  background-color: #f8f9ff;
  border-left: 4px solid #4a6bff;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  border-radius: 0 8px 8px 0;
  transition: transform 0.3s ease;
}

.lesson-card:hover {
  transform: translateX(5px);
}

.lesson-card h3 {
  margin-top: 0;
  color: #1a3dff;
}

.btn {
  display: inline-block;
  background: linear-gradient(135deg, #6B73FF 0%, #000DFF 100%);
  color: white;
  padding: 0.7rem 1.5rem;
  border-radius: 5px;
  text-decoration: none;
  font-weight: 600;
  margin-top: 1rem;
  border: none;
  cursor: pointer;
  transition: all 0.3s ease;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 13, 255, 0.2);
}

.progress-container {
  margin-bottom: 2rem;
}

.progress-bar {
  height: 10px;
  background-color: #e0e6ff;
  border-radius: 5px;
  margin-top: 0.5rem;
  overflow: hidden;
}

.progress {
  height: 100%;
  background: linear-gradient(135deg, #6B73FF 0%, #000DFF 100%);
  width: 25%;
  border-radius: 5px;
}

footer {
  text-align: center;
  padding: 2rem 0;
  margin-top: 2rem;
  color: #666;
  font-size: 0.9rem;
}

@media (max-width: 768px) {
  .content {
      grid-temp
💬 Ответ модели: DeepSeek V3

late-columns: 1fr;
  }

  nav ul {
      flex-direction: column;
      gap: 10px;
  }
}