style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body{
    width: 100vw;
    height: 100vh;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: black;
    color: white;
    background-image: url(https://media.giphy.com/media/xTiTniuHdUjpOlNo1q/giphy.gif?cid=ecf05e47cqtds5aael29epa85f8i853zxr7eygiyyc0e7roo&ep=v1_gifs_search&rid=giphy.gif&ct=g);
    background-repeat: no-repeat;
    background-size: cover;
}

h1{
    text-align: center;
    margin-top: 10%;
}

body .container-fluid{
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    top: 10%;
}
/* Input area */

form{
    width: 80%;
    background-color: rgba(255, 255, 255, 0.198);
    border-radius: 5px;
    display: flex;
    justify-content: space-between;
    margin-bottom: 10px;
}

form:hover{
    border: 2px solid white;
}

form input, button{
    background-color: transparent;
    font-size: 25px;
    color: white;
    border: 0;
    padding: 15px;
    cursor: pointer;
}

form input{
    width: 90%;
    height: 100%;
    text-align: center;
}

/* -list- */

#list-box{
    width: 80%;
    background-color: rgba(255, 255, 255, 0.198);
    border-radius: 5px;
}
 ol{
    font-size: 25px;
    font-weight: 600;
 }

ol li{
    display: flex;
    justify-content:space-between;
    align-items: center;
}

ol li i{
    padding: 15px;
    margin: 0 25px;
}

ol li i:hover{
    color: rgb(86, 235, 37);
}

.done{
    text-decoration: line-through;
    opacity: 60%;
}