body {
    font-family: Arial, sans-serif;
    background: #f0f0f0;
    padding: 20px;
}

#display {
    width: 100%;
    height: 120px;
    font-size: 20px;
    padding: 10px;
    box-sizing: border-box;
    margin-bottom: 15px;
}

.keyboard {
    display: inline-block;
    background: #ddd;
    padding: 10px;
    border-radius: 8px;
}

.row {
    display: flex;
    margin-bottom: 6px;
}

.key {
    min-width: 42px;
    height: 42px;
    margin: 2px;
    border: 1px solid #999;
    background: linear-gradient(#fff, #ccc);
    border-radius: 4px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    user-select: none;
    font-size: 16px;
}

.key.wide { min-width: 80px; }
.key.xwide { min-width: 220px; }

.key.active {
    background: linear-gradient(#aee, #7cc);
}

.key:active {
    background: linear-gradient(#ccc, #aaa);
}