/* Reset defaults */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Arial, Helvetica, sans-serif;
}

/* Body layout */
body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: linear-gradient(135deg, #74ebd5, #ACB6E5);
}

/* Calculator container */
.calculator {
  background: #4A90E2; /* nice blue */
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.2);
  width: 360px;
}

/* Display screen */
.output input {
  width: 100%;
  height: 60px;
  font-size: 24px;
  text-align: right;
  padding: 10px;
  border: none;
  border-radius: 10px;
  background: #f4f4f4;
  box-shadow: inset 2px 2px 5px #ccc, inset -2px -2px 5px #fff;
  margin-bottom: 15px;
}

/* Keypad layout: numbers left, operators right */
.keypad {
  display: grid;
  grid-template-columns: 3fr 1fr; /* numbers wider, operators narrower */
  gap: 10px;
}

.numbers {
  display: grid;
  grid-template-columns: repeat(3, 1fr); /* 3 numbers per row */
  grid-auto-rows: 60px;
  gap: 10px;
}

.operators {
  display: grid;
  grid-template-rows: repeat(4, 1fr); /* 4 operators stacked */
  gap: 10px;
}

/* Button styling */
.numbers input,
.operators input {
  font-size: 20px;
  font-weight: bold;
  border: none;
  border-radius: 12px;
  background: #e0e0e0; /* classic gray */
  color: black;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 3px 3px 6px #aaa, -3px -3px 6px #fff;
}

/* Hover effect */
.numbers input:hover,
.operators input:hover {
  background: #d1d1d1;
}

/* Active press effect */
.numbers input:active,
.operators input:active {
  box-shadow: inset 3px 3px 6px #aaa, inset -3px -3px 6px #fff;
}

/* Special buttons */
.numbers .clear {
  background: #ff7b7b;
  color: white;
}

.numbers .equals {
  background: #4caf50; /* green */
  color: white;
  grid-row: span 2;
}

/* 0 spans two columns */
.numbers input[value="0"] {
  grid-column: span 2;
}