* {
  margin: 0;
  padding: 0;
  box-sizing: border-box; 
  font-family: "Poppins", sans-serif;
}
body {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #d8e3f1, #b0c7e1);
}
.container {
  position: relative;
  max-width: 320px;
  width: 100%;
  border-radius: 16px;
  padding: 20px 24px 24px;
  background: #ffffff;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
}
.display {
  height: 100px;
  width: 100%;
  outline: none;
  border: none;
  text-align: right;
  margin-bottom: 20px;
  font-size: 30px;
  font-weight: bold;
  color: #333;
  background-color: #f9f9f9;
  border-radius: 8px;
  padding: 10px;
  box-shadow: inset 0 4px 6px rgba(0, 0, 0, 0.05);
  pointer-events: none;
}
.buttons {
  display: grid;
  grid-gap: 12px;
  grid-template-columns: repeat(4, 1fr);
}
.buttons button {
  padding: 15px;
  border-radius: 10px;
  border: none;
  font-size: 18px;
  cursor: pointer;
  font-weight: 500;
  transition: transform 0.2s ease, background-color 0.3s ease;
  background-color: #eaeff4;
  color: #444;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}
.buttons button:hover {
  background-color: #d0d7de;
}
.buttons button:active {
  transform: scale(0.96);
}
.operator {
  background-color: #2f9fff;
  color: #fff;
  font-weight: bold;
}
.operator:hover {
  background-color: #1d87e4;
}
.operator:active {
  transform: scale(0.96);
}