body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: linear-gradient(135deg, #2c3e50, #4ca1af);
}

.calculator {
    background: #1e1e2f;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.4);
}

#display {
    width: 100%;
    height: 60px;
    font-size: 24px;
    margin-bottom: 15px;
    text-align: right;
    border: none;
    border-radius: 10px;
    padding: 10px;
    background: #2d2d44;
    color: #fff;
    box-sizing: border-box;   
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 70px);
    gap: 12px;
}

button {
    height: 60px;
    font-size: 20px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: 0.2s;
    background: #3b3b5c;
    color: white;
}

/* Default buttons */
button {
    background: #3b3b5c;
    color: white;
}

/* Clear button */
.clear {
    background: #ff4757;
}

/* Delete button */
.delete {
    background: #ffa502;
}

/* Operator buttons */
.operator {
    background: #ff9f43;
}

/* Equals button */
.equals {
    background: #00d2d3;
    grid-column: 4;      /* keep in right column */
    grid-row: span 2;    /* make it taller */
}

/* Hover effect */
button:hover {
    transform: scale(1.05);
    opacity: 0.9;
}

button.zero {
    grid-column: span 2;
}

button:active {
    transform: scale(0.95);
}

.operator {
    background: #ff9f43;
}