One piece of feedback: it took me a moment to work out what 'pt', 'o' and 'fs' were. Single character variables are fine for algorithms but for demos you really want to use actual words.
I.e //app.js ...
//my-todo.js ....
"fz" is the typical shorthand used for font-size (at least by Emmet-style autocompleters). "fs" is used for font-style instead.