style.css

body {
    margin: 0;
    min-width: 250px;
}

* {
    box-sizing: border-box;
    font-family: Georgia, 'Times New Roman', Times, serif;
}

ul {
    margin: 0;
    padding: 0;
}

ul li {
    cursor: pointer;
    position: relative;
    padding: 12px 8px 12px 40px;
    background: #fff;
    font-size: 18px;
}

ul li:hover {
    background: rgba(106, 142, 35, 0.295);
}

ul li.checked {
    background: rgba(106, 142, 35, 0.295);
    color: #fff;
    text-decoration: line-through;
}

.close {
    position: absolute;
    right: 0;
    top: 0;
    padding: 12px 16px 12px 16px;
}

.close:hover {
    background-color: rgb(78, 104, 26);
    color: white;
}


.header {
    background-color: olivedrab;
    padding: 30px 40px;
    color: white;
    text-align: center;
}

.header:after {
    content: "";
    display: table;
    clear: both;
}

input {
    margin: 0;
    border: none;
    border-radius: 0;
    width: 70%;
    padding: 10px;
    float: left;
    font-size: 16px;
}

.addBtn {
    padding: 10px;
    width: 15%;
    background: rgba(164, 219, 53, 0.507);
    color: #fff;
    float: left;
    text-align: center;
    font-size: 16px;
    cursor: pointer;
    transition: 0.3s;
    border-radius: 0;
}

addBtn:hover {
    background-color: #fff;
}

.limparBtn {
    padding: 10px;
    width: 10%;
    background: #000;
    color: #fff; 
    float: left;
    text-align: center;
    font-size: 16px;
    cursor: pointer;
    transition: 0.3s;
    border: 0;
}

.addBtn {
    padding: 10px;
    width: 20%;
    background: rgba(164, 219, 53, 0.507);
    color: #fff;
    float: left;
    text-align: center;
    font-size: 16px;
    cursor: pointer;
    transition: 0.3s;
    border-radius: 0;
}