.bmr-calculator {
  max-width: 300px;
  font-family: "Roboto", sans-serif;
  padding: 8px 24px;
  box-shadow: 0 4px 8px -3px rgba(0, 0, 0, 0.3);
}

.bmr-calculator,
.bmr-calculator * {
  box-sizing: border-box;
}

.bmr-calculator h2 {
  text-align: center;
  background: #222;
  color: #fff;
  font-weight: 100;
  margin: -8px -24px;
  margin-bottom: 8px;
  padding: 16px;
}

.bmr-calculator form h3 {
  font-size: 15px;
  text-transform: uppercase;
  margin: 16px 0 10px 0;
}

.bmr-calculator form input[type="text"] {
  width: 100%;
  padding: 4px 16px;
  font-size: 24px;
  font-weight: bold;
  border: 1px solid #d5dbdd;
}

.bmr-calculator form input[type="text"].invalid {
  border: 1px solid red;
}

.bmr-calculator form {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.bmr-calculator form #female {
  margin-left: 20px;
}

.bmr-calculator form .height,
.bmr-calculator form .weight {
  position: relative;
}

.bmr-calculator form .unit {
  position: absolute;
  right: 20px;
  top: 50px;
  color: #777;
}

.bmr-calculator .result .calculate-btn {
  padding: 8px 24px;
  margin: 16px 0;
  font-size: 18px;
  font-weight: 100;
  text-transform: uppercase;
  border: none;
  background: #333;
  color: #fff;
  cursor: pointer;
  margin-bottom: 32px;
}

.bmr-calculator .result {
  text-align: center;
  color: #4e4e4e;
  font-size: 18px;
}

.bmr-calculator .result .calories {
  color: green;
  font-size: 38px;
  font-weight: 900;
  margin-right: 8px;
  vertical-align: middle;
}

.bmr-calculator .result .error-message {
  color: red;
  font-size: 14px;
  display: none;
}

.bmr-calculator .result .error-message.active {
  display: block;
}