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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f5f5f5;
}

.calculator {
    background-color: #333;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
    width: 300px;
    padding: 20px;
}

.display {
    margin-bottom: 20px;
}

#result {
    width: 100%;
    height: 60px;
    font-size: 24px;
    padding: 10px;
    text-align: right;
    border: none;
    border-radius: 5px;
    background-color: #eee;
    cursor: default;
}

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

button {
    padding: 15px 0;
    font-size: 18px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.number {
    background-color: #666;
    color: white;
}

.operator {
    background-color: #ff9500;
    color: white;
}

#equals {
    grid-column: span 2;
    background-color: #4CAF50;
}

button:hover {
    opacity: 0.8;
}

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