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

/* -------------------------
   Calculator container
------------------------- */
.calculator {
  width: 90%;
  max-width: 400px;
  background-color: #f0f0f0;
  border-radius: 15px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 15px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

/* -------------------------
   Display
------------------------- */
#display {
  background-color: #222;
  color: #fff;
  text-align: right;
  font-size: clamp(1.5rem, 4vw, 2rem);
  padding: 15px;
  border-radius: 10px;
  box-shadow: inset 0 -2px 5px rgba(0,0,0,0.3);
  overflow-x: auto;
}

/* -------------------------
   Button rows
------------------------- */
.button-row {
  display: flex;
  gap: 10px;
}

.clear-row {
  justify-content: center;
}

/* -------------------------
   Buttons
------------------------- */
button {
  flex: 1;
  height: clamp(50px, 10vw, 60px);
  font-size: clamp(1rem, 3vw, 1.5rem);
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.1s, filter 0.1s;
}

/* 0 button double width */
button.zero {
  flex: 2;
}

/* Number buttons */
button.number {
  background-color: #fff;
  color: #000;
}

/* Operator buttons */
button.operator {
  background-color: #000;
  color: #fff;
  font-weight: bold;
}

/* Hover effects */
button:hover {
  filter: brightness(1.1);
}

/* Active (pressed) effect */
button:active {
  transform: scale(0.95);
}