Nitpick: The JS heartbeat can be done in CSS3, otherwise this is great!
There are plenty of examples you could show in JS that would better show that it is where logic and behavior is stored. How about setting a textbox or showing an alert?
It should be done in CSS.
0. Not even sure if blink still exists, or if you can set it to animate, but my point stands that best practices are important.
Not if you want to show a simple JS example.