body {
  font-family: 'Open Sans', sans-serif;
  margin: 0;
  background-color: #fff;
  color: #333;
}

header {
  background-color: #22aa99;
  color: white;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 40px;
}

header a {
  color: white;
  text-decoration: none;
  margin-left: 20px;
  font-weight: 600;
}

.hero {
  text-align: center;
  padding: 60px 20px;
  background-color: #f4f4f4;
}

.feature-container {
  display: flex;
  justify-content: space-around;
  padding: 40px;
}

.feature-box {
  background-color: #f9f9f9;
  border: 1px solid #ddd;
  width: 28%;
  padding: 20px;
  border-radius: 5px;
}

footer {
  text-align: center;
  background-color: #22aa99;
  color: white;
  padding: 20px;
  margin-top: 40px;
}

.page-intro {
  text-align: center;
  padding: 40px;
  background-color: #f4f4f4;
}

.topic {
  max-width: 800px;
  margin: 30px auto;
  padding: 20px;
  background-color: #fafafa;
  border-left: 4px solid #22aa99;
}

.calc-section {
  max-width: 400px;
  margin: 40px auto;
  background-color: #f4f4f4;
  padding: 20px;
  border-radius: 8px;
  text-align: center;
}

.calc-section input {
  display: block;
  width: 90%;
  margin: 10px auto;
  padding: 10px;
  border: 1px solid #ccc;
  border-radius: 4px;
}

.calc-section button {
  background-color: #22aa99;
  color: white;
  border: none;
  padding: 10px 20px;
  cursor: pointer;
  margin-top: 10px;
  border-radius: 4px;
}

.calc-section button:hover {
  background-color: #1c9687;
}