body {
  background-color: #121212;
  color: #f7f7f7;
}

#container {
  width: 90%;
  max-width: 600px;
  margin: 0 auto;
  text-align: center;
  padding: 20px;
  border-radius: 4px;
  font-family: Arial, Helvetica, sans-serif;
}

#calculator {
  width: 90%;
  max-width: 400px;
  margin: 0 auto 15px auto;
  background-color: #2e2e2e;
  padding: 20px;
  border-radius: 4px;
  box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
}

form {
  width: 90%;
  max-width: 250px;
  margin: 0 auto;
}

input {
  width: 90%;
  padding: 10px;
  border: 1px solid #4d4d4d;
  border-radius: 4px;
  margin: 8px 0;
  box-sizing: border-box;
  font-size: 16px;
  outline: none;
  transition: all 0.2s ease;
}

input:focus {
  border: 1px solid #cccccc;
}

button {
  width: 90%;
  background-color: #919191;
  color: #333;
  padding: 14px 20px;
  margin: 8px 0;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 16px;
  outline: none;
  transition: all 0.2s ease;
}

button:hover {
  background-color: #b0b0b0;
}

h2 {
  margin-top: 0;
}

#results {
  width: 90%;
  max-width: 250px;
  margin: 0 auto;
  text-align: center;
  font-size: 25px;
}

#banner {
  text-align: center;
  max-width: 100%;
  height: auto;
}