body {
    font-family: Arial, sans-serif;
    background-color: #f0f8ff;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.calculator {
    border: 2px solid #333;
    border-radius: 10px;
    padding: 20px;
    background: #fff;
    box-shadow: 2px 2px 10px #bbb;
    width: 280px;
}

#result {
    width: 100%;
    height: 40px;
    font-size: 1.5em;
    margin-bottom: 10px;
    padding: 5px;
    text-align: right;
    border: 1px solid #ddd;
    border-radius: 4px;
}

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

button {
    font-size: 1.2em;
    padding: 10px;
    border: none;
    border-radius: 4px;
    background: #f8f9fa;
    cursor: pointer;
    transition: background 0.2s;
}

button:hover {
    background: #dbeafe;
}

.equal {
    grid-column: span 4;
    background: #22d3ee;
    color: #fff;
    font-weight: bold;
}