Is it possible to develop UI5 application with just text editor?

Hi Guys,

I'm following UI5 developer guide to build a simple application. Below is the snapshot:

I thought I was done. And tried to preview this index.html in the browser. But there's a lot of errors in the console.

And I see there're some differences between what i did and eclipse generated project. In eclipse generated project,

there're some java resources and pre-configured web.xml and some other stuff.

So my questions is :

1. Is it possible I just use sap UI5 the same way I use other js libraries( e.g. jquery, angular ... ) ?

2. why is sap ui5 runtime such a big library? the file size is about hundred Mbs, normal js library only hundred Kbs.