html, body {
    height: 100%; /* Ensure the body and html elements fill the viewport height */
    margin: 0; /* Remove default margins */
    font-family: sans-serif;
    text-align: center;
    background-image: url("https://static.scientificamerican.com/sciam/cache/file/01441EC0-AE7C-4F92-94583DF9D6C8EAFF_source.jpg?w=1200");
    background-size: cover; /* Makes the background cover the entire screen */
    background-repeat: no-repeat; /* Prevents repeating */
    background-position: center; /* Centers the background image */
    background-color: rgba(255, 255, 255, 0.45); /* Adds a 50% white overlay */
    background-blend-mode: overlay; /* Blends the overlay with the background image */
}
a {
    color: red;
    text-decoration: none;
}
.key {
    color: #2c9949;
}
.quizlet {
    color: blue;
}