body {
    font-family: Arial, sans-serif;
    background: #ffffff;
    /* White background */
    color: #000;
    /* Black text */
    text-align: center;
    padding: 20px;
}

h1 {
    margin-bottom: 20px;
}

.tabs {
    margin-bottom: 25px;
}

.tab-btn {
    padding: 10px 20px;
    margin: 5px;
    border: none;
    background: #e0e0e0;
    color: #000;
    cursor: pointer;
    border-radius: 5px;
}

.tab-btn.active {
    background: #00bcd4;
    color: white;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.display {
    font-size: 48px;
    margin: 20px auto;
    padding: 20px;
    background: #f6f6f6;
    /* light grey block */
    border-radius: 10px;
    color: #000;
    width: 60%;
    max-width: 350px;
}

.btn-group button {
    padding: 10px 20px;
    margin: 10px;
    border: none;
    border-radius: 5px;
    background: #00bcd4;
    color: white;
    cursor: pointer;
}