Why is the font size not changing?

Question

Angular

There is an angular project (version 2.0+).
Link: https://stackblitz.com/edit/angular-dserds?file=sr...
The question is this. Why doesn't the text change its size when clicked? NaN comes out instead

Answer 1

And where do you have the fontSizePx property in the my-app component, which, according to the template, should be responsible for the size? - I don't see anything like that. We add, everything is ok .