styles.css

html {
    margin: 0;
    font-size: 16px;
}

body {
    width: 95%;
    background-color: green;
    font-family: "Coiny", sans-serif;
    color: white;
}

#outer {
    width: 16rem;
    /* You can define it by % also */
    height: 16rem;
    /* You can define it by % also */
    position: relative;
    border: 1px solid black;
    border-radius: 50%;
}

#inner {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: white;
    top: 25%;
    left: 25%;
    /* of the container */
    width: 50%;
    /* of the container */
    height: 50%;
    /* of the container */
    position: relative;
    border: 1px solid black;
    border-radius: 50%;
    font-size: 4rem;
    color: black;
    text-align: center;
}

ul {
    text-align: center;
}

li {
    font-size: 1.75rem;
    text-align: left;
}