Why doesn't simple v-on:click work?

Question

Vue.js

Hey!
Why doesn't the standard v-on:click work ?
You have to add crutches from JS. This is how it works:

So why doesn't it work? :

p.s. Pushed the button inside the vue instance, still doesn't work

jsfiddle

Answer 1

Well, firstly, you need to put the button in the template too, so that Vue knows about it.
And secondly v-on:click="seen = !seen"
https://www.youtube.com/watch?v=037TFFtE-qo