body {
    background-color: #121212;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: Arial, sans-serif;
}

.calculator {
    background-color: #1e1e1e;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.5);
}

#display {
    width: 100%;
    height: 60px;
    background-color: #000;
    color: #fff;
    font-size: 30px;
    text-align: right;
    padding: 10px;
    border: none;
    border-radius: 8px;
    box-sizing: border-box;
    margin-bottom: 15px;
}

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

.btn {
    padding: 20px;
    font-size: 20px;
    border: none;
    border-radius: 8px;
    background-color: #333;
    color: white;
    cursor: pointer;
}

.btn:hover { background-color: #444; }
.operator { background-color: #ff9500; }
.operator:hover { background-color: #e08400; }
.clear { background-color: #ff3b30; }
.equal { background-color: #34c759; grid-row: span 2; height: 100%; }