body {
  font-family: "Arial", sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #f0f4f8; /* Light blue-grey background */
  margin: 0;
  padding: 20px;
  box-sizing: border-box;
  color: #333;
}

.container {
  background-color: #ffffff;
  border-radius: 15px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  padding: 35px;
  max-width: 1200px;
  width: 100%;
  text-align: center;
  animation: fadeIn 0.8s ease-out;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

h1 {
  color: #1a73e8; /* Google Blue heading */
  margin-bottom: 25px;
  font-size: 2.5em;
  position: relative;
  padding-bottom: 10px;
}
h1::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 0;
  transform: translateX(-50%);
  width: 80px;
  height: 4px;
  background-color: #4285f4; /* Lighter Google Blue accent */
  border-radius: 2px;
}

.instructions {
  background-color: #e8f0fe; /* Very light blue for instructions */
  border: 1px solid #d2e3fc;
  border-radius: 8px;
  padding: 15px 20px;
  margin-bottom: 25px;
  text-align: left;
  font-size: 0.9em;
  color: #1a73e8;
  line-height: 1.5;
}
.instructions h3 {
  margin-top: 0;
  color: #0c4a8f;
  font-size: 1.2em;
  margin-bottom: 10px;
}
.instructions ul {
  margin: 0;
  padding-left: 20px;
}
.instructions li {
  margin-bottom: 5px;
}

.input-group {
  margin-bottom: 15px;
  text-align: left;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.input-group label {
  font-weight: bold;
  color: #555;
  min-width: 80px;
}

.input-group input[type="number"],
.input-group select {
  flex-grow: 1;
  padding: 12px 10px;
  border: 1px solid #ccc;
  border-radius: 6px;
  font-size: 1em;
  box-sizing: border-box;
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
  min-width: 120px;
}

.input-group input[type="number"]:focus,
.input-group select:focus {
  border-color: #4285f4;
  outline: none;
  box-shadow: 0 0 0 3px rgba(66, 133, 244, 0.2);
}

.dimensions-input-area {
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  padding: 20px;
  margin-top: 20px;
  background-color: #fcfcfc;
}
.dimensions-input-area h3 {
  margin-top: 0;
  color: #4a4a4a;
  font-size: 1.2em;
  margin-bottom: 15px;
}

.btn-calculate {
  padding: 15px 30px;
  background-color: #34a853; /* Google Green */
  color: white;
  border: none;
  border-radius: 8px;
  font-size: 1.1em;
  cursor: pointer;
  transition: background-color 0.3s ease, transform 0.2s ease;
  text-transform: uppercase;
  font-weight: bold;
  letter-spacing: 0.5px;
  width: 100%;
  margin-top: 20px;
}
.btn-calculate:hover {
  background-color: #2e8b4e;
  transform: translateY(-2px);
}

.result-output {
  margin-top: 30px;
  padding: 20px;
  background-color: #e6f4ea; /* Light green for results */
  border: 1px solid #cce3d1;
  border-radius: 8px;
  text-align: left;
  min-height: 80px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  animation: slideInUp 0.5s ease-out;
  box-sizing: border-box;
}
@keyframes slideInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.result-output p {
  margin: 8px 0;
  font-size: 1.05em;
  color: #444;
}

.result-output .highlight {
  font-size: 1.6em;
  font-weight: bold;
  color: #1a73e8; /* Google Blue */
  margin-top: 10px;
  margin-bottom: 10px;
}
.error-message {
  color: #dc3545;
  font-weight: bold;
  margin-top: 10px;
  text-align: center;
}

/* Responsive adjustments */
@media (max-width: 600px) {
  .container {
    padding: 20px;
  }
  h1 {
    font-size: 2em;
  }
  .btn-calculate {
    font-size: 1em;
    padding: 12px 20px;
  }
  .result-output .highlight {
    font-size: 1.4em;
  }
  .input-group {
    flex-direction: column;
    align-items: flex-start;
    gap: 5px;
  }
  .input-group input,
  .input-group select {
    width: 100%;
    min-width: unset;
  }
  .input-group label {
    margin-bottom: 0px;
  }
}