body {
  font-family: 'Roboto', sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f5f5f5;
  color: #333;
}

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

header {
  background-color: #007bff;
  color: white;
  text-align: center;
  padding: 30px 0;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

h1 {
  font-size: 4em;
  margin: 0;
  font-weight: 500;
}

h2 {
  font-size: 2.8em;
  color: #555;
  margin-bottom: 30px;
}

p {
  font-size: 1.3em;
  line-height: 1.7;
  color: #777;
}

ul {
  list-style-type: none;
  padding: 0;
}

li {
  margin-bottom: 18px;
  font-size: 1.3em;
  color: #666;
  border-left: 3px solid #007bff;
  padding-left: 15px;
}

footer {
  background-color: #007bff;
  color: white;
  text-align: center;
  padding: 20px 0;
  margin-top: 60px;
  font-size: 1.2em;
  box-shadow: 0 -4px 15px rgba(0, 0, 0, 0.1);
}

.btn {
  display: block;
  margin: 30px auto 0;
  padding: 10px 20px;
  font-size: 1.2em;
  background-color: #007bff;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

.btn:hover {
  background-color: #0056b3;
}

/* Анимация */
@keyframes fadeIn {
  from {
      opacity: 0;
      transform: translateY(30px);
  }
  to {
      opacity: 1;
      transform: translateY(0);
  }
}

.operation, .properties, .numbers {
  animation: fadeIn 1s ease-in-out;
}