vue/examples/todos/custom.css

#todoapp.all [data-filter="all"],
#todoapp.active [data-filter="active"],
#todoapp.completed [data-filter="completed"] {
    font-weight: bold;
}

#todoapp.active #todo-list li.completed {
    display: none;
}

#todoapp.completed #todo-list li:not(.completed) {
    display: none;
}