.multi-tools-wrapper {
  font-family: Arial, sans-serif;
  max-width: 400px;
  margin: 30px auto;
  padding: 20px;
  border: 1px solid #ddd;
  border-radius: 8px;
  background: #fefefe;
}
#calc-display {
  width: 100%;
  font-size: 1.5em;
  padding: 10px;
  margin-bottom: 10px;
}
#calc-buttons button {
  width: 23%;
  padding: 10px;
  margin: 2px;
  font-size: 1.2em;
}
#stopwatch {
  font-size: 2em;
  margin: 10px 0;
}