body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: #1c1c1e;  /* Dark background for that sleek, modern feel */
  color: #fff;  /* Text color is white to contrast with dark background */
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background-color: #333; /* Dark background for the calculator */
  padding: 30px;
  border-radius: 30px;
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.2);
  display: flex;
  flex-direction: column;
  width: 320px;
  text-align: center;
}

#result {
  width: 100%;
  padding: 20px;
  font-size: 2.5em;
  text-align: right;
  background-color: #2c2c2e; /* Slightly lighter background for the input field */
  border-radius: 15px;
  border: none;
  color: #fff;  /* White text */
  box-shadow: inset 0 4px 6px rgba(0, 0, 0, 0.2);
  margin-bottom: 20px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 15px;
}

.button {
  background-color: #ff9500;  /* Bright orange color for buttons */
  font-size: 1.5em;
  border-radius: 15px;
  padding: 20px;
  border: none;
  color: #fff;  /* White text on buttons */
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
  transition: all 0.3s ease;
}

.button:hover {
  background-color: #ff7f00;  /* Slightly darker orange on hover */
  box-shadow: 0 6px 15px rgba(0, 0, 0, 0.3);
}

.button:active {
  background-color: #e06c00;  /* Even darker orange on active click */
  box-shadow: inset 0 4px 10px rgba(0, 0, 0, 0.3);
}

button:focus {
  outline: none;
}

button:disabled {
  background-color: #555;
  color: #bbb;
}

button:active:disabled {
  background-color: #666;
}

#result:disabled {
  background-color: #2c2c2e;
}