todo.css

/* Styling for new todo item input */
.created-checkbox:not(:checked) ~ .todo-input {
    position: absolute;
    top: 0;
    padding-left: calc(15px + 40px);
    box-shadow: inset 0 -2px 1px rgba(0,0,0,0.03);
}
.created-checkbox:not(:checked) ~ .todo-input,
.created-checkbox:not(:checked) ~ .created-checkbox-label {
    border-bottom: 1px solid #e6e6e6;
}

/* Mark as done/not done */
.done-checkbox,
.mark-done-checkbox-label,
.mark-undone-checkbox-label {
    display: none;
}

.mark-done-checkbox-label,
.mark-undone-checkbox-label {
    cursor: pointer;
    padding-top: 13px;
    padding-bottom: 11px;
    border-bottom: 1px solid #ededed;
}
/* Show mark as done if item is created and not marked as done yet */
.created-checkbox:checked ~ .done-checkbox:not(:checked) ~ .mark-done-checkbox-label {
    display: inline-block;
}
/* Show mark as undone if item is created and marked as done */
.created-checkbox:checked ~ .done-checkbox:checked ~ .mark-undone-checkbox-label {
    display: inline-block;
}

/* Item creation */
.created-checkbox-label {
    position: absolute;
    top: 0;
    right: 0px;
    width: 40px;
    cursor: pointer;
    background: #d6d6d6;
    font-weight: bold;
    padding: 22px;
    padding-left: 10px;
    padding-right: 10px;
    text-align: center;
}
.created-checkbox-label:hover {
    background: #ddd;
}
/* Don't allow creating empty items */
input:not(:valid) ~ .created-checkbox-label {
    pointer-events: none;
}

.created-checkbox {
    display: none;
}
.created-checkbox:checked + input {
    border: none;
}

/* Item creation state */
.created-checkbox:checked ~ .todo > .todo-input,
.created-checkbox:checked ~ .todo > .created-checkbox-label {
    display: inline-block;
}

.created-checkbox:checked ~ .created-checkbox-label {
    display: none !important;
}

/* Item deletion */

.deleted-checkbox-label,
.deleted-checkbox {
    display: none;
}

.deleted-checkbox-label {
    display: none;
	width: 60px;
	margin: auto 0;
	font-size: 30px;

	transition: color 0.2s ease-out;
    text-align: center;
    color: transparent;
    border-bottom: 1px solid #ededed;
    box-sizing: border-box;
    /* unequal padding because the x icon itself is not centered on the line of text*/
    padding-top: 17px;
    padding-bottom: 28px;
    cursor: pointer;
}

.deleted-checkbox-label:hover {
	color: #af5b5e !important;
}

.created-checkbox:checked ~ .deleted-checkbox-label {
    display: inline-block;
}

/* Show the delete icon on hover over any of the item elements */
.created-checkbox:checked ~ .deleted-checkbox-label:hover,
.created-checkbox:checked ~ :not(.todo):hover ~ .deleted-checkbox-label {
    color: #cc9a9a;
}

/* If item is deleted hide its elements */
.deleted-checkbox:checked ~ :not(.todo) {
    display: none !important;
}

/* Hide items marked as done if filter is active */
.active-filter:target .created-checkbox:checked ~ .done-checkbox:checked ~ .todo-input,
.active-filter:target .created-checkbox:checked ~ .done-checkbox:checked ~ .mark-done-checkbox-label,
.active-filter:target .created-checkbox:checked ~ .done-checkbox:checked ~ .mark-undone-checkbox-label,
.active-filter:target .created-checkbox:checked ~ .done-checkbox:checked ~ .deleted-checkbox-label {
    display: none !important;
}

/* Hide items not marked done if filter is completed */
.completed-filter:target .created-checkbox:checked ~ .done-checkbox:not(:checked) ~ .todo-input,
.completed-filter:target .created-checkbox:checked ~ .done-checkbox:not(:checked) ~ .mark-done-checkbox-label,
.completed-filter:target .created-checkbox:checked ~ .done-checkbox:not(:checked) ~ .mark-undone-checkbox-label,
.completed-filter:target .created-checkbox:checked ~ .done-checkbox:not(:checked) ~ .deleted-checkbox-label {
    display: none !important;
}

/* Indicate currently selected filter */
.active-filter:target .filter-active,
.completed-filter:target .filter-completed,
.completed-filter:not(:target) .active-filter:not(:target) .filter-all {
    border-color: rgba(175, 47, 47, 0.2);
}

/* items-left counter */
body  {
    counter-reset: items-left;
}
.created-checkbox:checked ~ .deleted-checkbox:not(:checked) ~ .done-checkbox:not(:checked) ~ .items-left-counter-helper {
    /* items-left-counter-helper is an empty element that's not hidden by filters */
    counter-increment: items-left;
}
#items-left:before {
    content: counter(items-left);
}

/* Basic Item styles */

#todo-1 {
    position: relative;
    padding-top: 65px;
}

#todo-0 > :not(.todo) { /* todo 0 is used to bootstrap the todo-1 as visible (because todo 0 is marked as created) */
    display: none;
}
.todo-input {
    white-space: pre-line;
    word-break: break-all;
    padding: 15px 60px 15px 15px;
    margin-left: 45px;
    display: block;
    line-height: 1.2;
    transition: color 0.4s;
    border: 0;
    border: none;
    border-bottom: 1px solid #ededed;

    background: rgba(0, 0, 0, 0.003);
    position: relative;
    margin: 0;
    width: calc(100% - 175px);
    font-size: 24px;
    font-family: inherit;
    font-weight: inherit;
    line-height: 1.4em;
    outline: none;
    color: inherit;
    -webkit-font-smoothing: antialiased;
    -moz-font-smoothing: antialiased;
    font-smoothing: antialiased;
}

.todo-input,
.created-checkbox-label {
    display: none;
}

.todo {
    display: flex;
    width: 100%;
    flex-wrap: wrap;
}


@media (max-width: 600px) {
    body {
        padding: 5px;
    }
}