body {
  font-family: Arial, sans-serif;
  background: #d3d3d3;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background: #ececec;
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 0 20px rgba(0,0,0,0.2);
  width: 320px;
}

.display {
  background: #b6e2f7;
  padding: 20px;
  text-align: right;
  font-size: 2em;
  border-radius: 10px;
  margin-bottom: 15px;
  min-height: 60px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

button {
  padding: 20px;
  font-size: 1.2em;
  border: none;
  border-radius: 10px;
  background: #f0f0f0;
  box-shadow: inset 0 -2px 2px rgba(0,0,0,0.1);
  cursor: pointer;
  transition: background 0.2s;
}

button:hover {
  background: #ddd;
}

.clear {
  background: #f87171;
  color: white;
}

.equal {
  background: #facc15;
}

.back {
  background: #94a3b8;
  color: white;
}

.display {
  position: relative;
  background-color: #b3e5fc;
  height: 100px;
  border-radius: 10px;
  overflow: hidden;
}

.display iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: none;
}