body{
  background:#f7f7fa;
  display:flex;
  justify-content:center;
  align-items:center;
  height:100vh;
  font-family:Arial;
}

.calculator{
  background:#f4f4f5;
  padding:25px;
  border-radius:20px;
  box-shadow:0 10px 25px rgba(0,0,0,0.6);
  width:100%;
  max-width:320px;
}

#display{
  width:100%;
  height:60px;
  border:none;
  border-radius:10px;
  margin-bottom:20px;
  font-size:22px;
  padding:10px;
  background:#c0c2c6;
  color:black;
  text-align:right;
  box-sizing:border-box;
}

.buttons{
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:12px;
}

button{
  height:60px;
  border:none;
  border-radius:12px;
  font-size:20px;
  cursor:pointer;
  background:#2b2f3a;
  color:white;
  box-shadow:0 4px 10px rgba(255,255,255,0.5);
  transition:transform 0.08s, box-shadow 0.08s;

  -webkit-tap-highlight-color:transparent;
  touch-action:manipulation;
  user-select:none;
}

button:hover{
  transform:scale(1.05);
}

button:active{
  transform:scale(0.95);
  box-shadow:0 2px 5px rgba(0,0,0,0.3);
}

.operator{
  background:#f39c12;
}

.equal{
  background:#1d8bd5;
}

.clear{
  background:#d35137;
  grid-column:span 2;
}

.backspace{
  background:#d35137;
  grid-column:span 2;
}