body {
  background-color: #f2f2f2;
  font-family: "Inter", sans-serif;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: 0;
  color: #333;
}

.title {
  font-size: 2rem;
  margin-bottom: 2rem;
}

.calculator-preview {
  background-color: #ffffff;
  padding: 2rem;
  border-radius: 20px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.display {
  background-color: #e0e0e0;
  color: #333;
  font-size: 2rem;
  padding: 1rem;
  border-radius: 12px;
  margin-bottom: 1.5rem;
  text-align: right;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
  min-height: 2.3rem;
}

.button-grid {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  width: 300px;
  justify-content: center;
}

.btn {
  width: 60px;
  height: 60px;
  background-color: #f9f9f9;
  border: none;
  padding: 1rem;
  border-radius: 12px;
  font-size: 1.3rem;
  color: #000;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  justify-content: center;
  align-items: center;
  -webkit-tap-highlight-color: transparent;
}

.btn:hover {
  transform: scale(0.95);
  box-shadow: inset 0 2px 5px rgba(0, 0, 0, 0.1);
}

.btn:active {
  background-color: #c3e6af;
  transform: scale(0.9);
  box-shadow: inherit 0 4px 8px rgba(0, 0, 0, 0.15);
  transition: none;
}

.btn.accent {
  background-color: #d1f5c0;
  color: #1a1a1a;
}

.active-operator {
  background-color: #d1f5c0;
  color: #1a1a1a;
  box-shadow: 0 0 8px #d1f5c0;
  border: 2px solid #86c88f;
}

.btn.equals {
  background-color: #86c88f;
  color: #fff;
}

.btn.equals:hover {
  background-color: #74b57e;
}

.btn.clear {
  background-color: #d1f5c0;
  color: #226;
}

.btn.clear:hover {
  background-color: #d1f5e1;
}

.btn.del {
  background-color: #d1f5c0;
  color: #226;
}

.btn.del:hover {
  background-color: #d1f5e1;
}

.btn.flash {
  background-color: #a0a0a0;
  transition: background-color 0.1s ease-out;
}