styles.css

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

html {
    min-height: 100vh;
    height: auto;
    background-color: #d2c8d2;
    background-image: linear-gradient(0deg, #d2c8d2 0%, #d7e6e6 19%, #ffffff 39%, #ffffff 60%, #ffffff 80%, #cdddde 100%);
}

body {
    font-size: 16px;
    font-family: "Montserrat", sans-serif;
    font-optical-sizing: auto;
    color: #333;
}

.app {
    padding: 0 0 2em;
    width: 600px;
    margin: auto;
}

.DateTime {
    margin: 40px 0;
    color: #333;
}

.DateTime__Date {
    display: block;
    font-size: 20px;
    font-weight: 300;
    text-align: center;
    margin-bottom: 8px;
}

.heading {
    display: block;
    font-size: 22px;
    font-weight: 300;
    text-align: center;
    margin-bottom: 8px;
}

.DateTime__Time {
    display: block;
    font-size: 48px;
    font-weight: 700;
    text-align: center;
}

.TextBox {
    height: 50px;
    border: 0;
    width: 100%;
    background: #fafafa;
    border: 1px solid #ddd;
    color: #333;
    outline: none;
    font-size: 15px;
    padding: 0 15px;
    font-family: inherit;
    border-top-right-radius: 5px;
    border-top-left-radius: 5px;
}

.TextBox::placeholder {
    color: rgba(0,0,0,0.3);
}

.TextBox:focus {
    border: 1px solid rgba(210, 203, 185, 0.5);
}

.Todolist {
    list-style-type: none;
    padding: 0;
}

.Todo {
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-height: 50px;
    border: 1px solid #eee;
    border-top: 0;
    color: #333;
    background-color: #fff;
    cursor: pointer;
    position: relative;
}

.Todo__Check {
    padding: 0 1em;
    width: 50px;
    height: 50px;
    line-height: 3.7;
}

.Todo__Check i {
    display: inline-block;
    height: 1em;
    width: 1em;
    border: 1px solid #ccc;
    border-radius: 50%;
    cursor: pointer;
}

.Todo__Task {
    flex: 1;
    padding: 13px 1em 13px 0;
    line-height: 1.5;
}

.Todo__Delete, .Todo__Edit {
    border: none;
    background: none;
    margin: 0 1em;
    font-size: 14px;
    color: #ccc;
    display: none;
}

.Todo:hover {
    background: #fafafa;
}

.Todo:hover .Todo__Delete,
.Todo:hover .Todo__Edit {
    display: block;
}

.Todo--checked .Todo__Check i {
    background: #27ae60;
    border: 2px solid #27ae60;
}

.Todo--checked .Todo__Task {
    text-decoration: line-through;
    color: #ccc !important;
}