styles.css

body {
    background: gainsboro;
    text-align: center;
    margin-top: 50px;
    color: black;
}

#container {
    background: navajowhite;
    width: 500px;
    margin: 0 auto;
    border: 2px solid black;
    padding: 24px;
    border-radius: 16px;
}

#input-text {
    width: 200px;
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    margin-right: 5px;
    font-size: 20px;
}

#input-button {
    font-size: 20px;
    cursor: pointer;
    transition: 0.4s;
    padding: 10px;
    border: none;
    border-radius: 5px;
    background-color: rosybrown;
    color: white;
}

hr {
    border: 1px solid black;
}

#header {
    margin: 5px;
    font-size: 20px;
    text-align: center;
}

h1 {
    margin-bottom: 20px;
}

#input-button:hover {
    background-color: white;
    color: black;
}

ul {
    list-style: none;
    padding: 0;
    margin-top: 20px;
    text-align: left;
}

li {
    border: 2px solid black;
    border-radius: 5px;
    margin-bottom: 10px;
    padding: 10px;
    margin-top: 10px;
}

.edit-button,
.delete-button,
.complete-button {
    float: right;
    color: red;
    cursor: pointer;
    margin: 3px 5px;
    border: none;
    background: none;
}

.completed {
    text-decoration: line-through;
    color: gray;
    border: 2px solid gray;
}