.due-calculator {
  border: 2px solid #e5e5e5;
  border-radius: 12px;
  padding: 20px;
  max-width: 550px;
  background: #ffffff;
  font-family: "Open Sans", Arial, sans-serif;
  box-shadow: 0 2px 6px rgba(0,0,0,0.05);
  margin: 30px auto;
}

.due-calculator h3 {
  margin: 0 0 10px 0;
  font-weight: 700;
}

.due-calculator label {
  display: block;
  margin: 12px 0 6px;
  font-weight: 600;
  color: #333;
}

.due-calculator input[type="date"],
.due-calculator input[type="number"] {
  padding: 10px;
  width: 100%;
  font-size: 16px;
  border: 1px solid #ccc;
  border-radius: 6px;
  background: #fafafa;
  transition: border-color 0.2s;
}

.due-calculator input:focus {
  outline: none;
  border-color: #80c7cc;
  background: #fff;
}

.due-calculator button {
  margin-top: 14px;
  background-color: #80c7cc;
  color: #fff;
  padding: 12px 20px;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-weight: bold;
  font-size: 16px;
  transition: background 0.3s, transform 0.1s;
  display: inline-block;
}

.due-calculator button:hover {
  background-color: #5fa7aa;
  transform: translateY(-1px);
}

.due-result {
  margin-top: 20px;
  background: #f9f9f9;
  padding: 18px;
  border: 1px solid #ddd;
  border-radius: 8px;
  font-size: 16px;
  line-height: 1.6;
  color: #444;
}

.due-result strong {
  color: #222;
}

.due-result .muted {
  color: #666;
  font-size: 14px;
}