style.css

body {
    padding: 0;
    margin: 0;
    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    font-size: 24px;
    font-weight: 300;
}

* {
    box-sizing: border-box;
}

.todo-list {
    list-style: none;
    margin: 0;
    padding: 0;
}

.todo-list > li {
    display: inline-block;
    width: 100%;
    height: 2.2em;
    line-height: 2.2em;
    border-bottom: 1px solid #dddddd;
}

.todo-list > li:first-child {
    border-top: 1px solid #dddddd;
}

.action {
    display: inline-block;
    height: 100%;
    width: 2em;
    float: left;
    cursor: pointer;
    text-align: center;
    color: #cccccc;
}

.completed .action.checkbox {
    color: #66CD00;
}

.title {
    display: inline-block;
    width: calc(100% - 6em);
    float: left;
}

.completed .title {
    text-decoration: line-through;
    color: #888888;
}

.todo-input {
    height: 2em;
    line-height: 2em;
}

input {
    font-size: 24px;
    width: 78%;
    height: 80%;
}

.create-todo {
    position: relative;
    height: 80%;
    width: 20%;
    margin: 0;
    padding: 0;
    border: 0;
    font-size: 24px;
    color: #ffffff;
    background-color: #2d97d2;
    border-radius: 5px;
}

.single-todo {
    padding: 1em;
}