body {
    font-family: Arial, sans-serif;
    background: #f4f4f4;
    display: flex;
    justify-content: center;
    padding-top: 40px;
    margin: 0;
}

.calculator {
    width: 360px;
    background: white;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 0 15px rgba(0,0,0,0.2);
}

#display {
    width: 100%;
    height: 60px;
    font-size: 26px;
    padding: 10px;
    border-radius: 10px;
    border: 1px solid #ccc;
    margin-bottom: 10px;
    background: #fafafa;
}

#historyLine {
    text-align: right;
    margin-bottom: 8px;
    color: #555;
}

.mode-label {
    display: block;
    margin-bottom: 12px;
    font-weight: bold;
}

.keypad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}

.keypad button {
    padding: 15px;
    font-size: 18px;
    border: none;
    border-radius: 10px;
    background: #e6e6e6;
    cursor: pointer;
    transition: 0.2s;
}

.keypad button:active {
    background: #ccc;
}

.operator {
    background: #ffcc80;
}

.equals {
    background: #7bdc7b;
    font-weight: bold;
}

#historyList {
    max-height: 130px;
    overflow-y: auto;
    background: #fafafa;
    margin-top: 15px;
    padding: 10px;
    border-radius: 10px;
}

#historyList li {
    padding: 6px;
    border-bottom: 1px solid #ddd;
    cursor: pointer;
}