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

.calculator {
    width: 360px;
    background: #1e1e1e;
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 0 20px #000;
}

.display {
    color: white;
    font-size: 2.5rem;
    text-align: right;
    padding: 20px 10px;
    background: #1e1e1e;
    border-bottom: 1px solid #333;
    height: 60px;
}

.operation {
    color: #aaa;
    font-size: 1.2rem;
    text-align: right;
    padding: 10px 10px;
    height: 30px;
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding-top: 20px;
}

.buttons button {
    background: #2e2e2e;
    border: none;
    color: white;
    font-size: 1.3rem;
    padding: 20px;
    border-radius: 10px;
    cursor: pointer;
    transition: background 0.2s;
}

.buttons button:hover {
    background: #3e3e3e;
}

.buttons button.operator {
    color: #66aaff;
}

.buttons button.action {
    color: #ffaa66;
}

.buttons button.equal {
    background: #b30000;
    color: white;
}

.buttons button.equal:hover {
    background: #cc0000;
}