How do I acquire users?

I can't answer your question because I have no experience with this, but I'd like to ask you: How did you acquire those first 200 users in the first place? I'd like to publish an application myself sometime in the near-future, but one of my "fears" is that nobody will use it--and I don't know how to acquire users.

By the way, nice job with the application. This is very impressive work for anybody, but especially for a 17 year old. Did you work on this entirely by yourself?

Through marketing and hard work. Good luck.

Out of curiosity I've followed the link to see what it is. I'm pretty sure before-hand that I'm not in your target audience, so this will be less useful that it might, but I will give you my reactions as I go.

Understand ... I appreciate that you've done a lot of work, and the implementation looks excellent. There's a lot here that's good, but I suspect it's entirely in the implementation, and not in the targeted marketing.

So ...

Firstly visit ... two thirds of the screen tells me this is "DomeCode". That is great branding, but it doesn't help me understand what it is, what it does, what it does for me, or why I should even scroll down.

In writing, every sentence should be a reason to read the next one.

It also says "Get more. With less hassle. Free & Open Source."

That tells me nothing that helps me understand why I should look further. There is no indication of what it will do for me.

I scroll down one page. Taking the text there phrase by phrase:

"DomeCode is an open source platform ..."

I don't care ... what does it do for me? Being Open Source is something I would care about once I've thought "This is useful, should I use it?" On my first visit, first impression, this is not something I care about.

"... you can advance your coding journey ..."

I don't know what this means. Is it a learning platform? A Coding Dojo? Somewhere I can develop advance projects? Who is this aimed at? Beginners? Professionals? Developers? Non-coders who need to learn a little?

" ... with compiled resources ..."

I don't know what this means. You've gather things that coders will need? You've made things that programmers will need?

"... to learn programming concepts, ..."

As a beginner?

" ... take notes, plan tasks, ..."

What kinds of tasks ... coding? Contracts? Household chores?

"... practice coding problems, ..."

Set by whom? Found where? In what language or languages? Are they graded? Are there answers?

"... discuss interesting stuff on the forum, meet other developers ..."

Only if there are developers ... yes, chicken and egg, I know.

And what sort of other developers? Front-End? Back-End? SysOp? Embedded?

"... and most all even get to listen to music conveniently ..."

At this point, personally, I'm out. I don't listen to music while I code.

OK, I'll stop there and summarise.

When I look at the first page I can't see any reason to read further. When I read the second page I have more questions than answers, and no reason to read further, and then I end up feeling it's just not for me.

But maybe it's not for me ... as I said, I'm probably not your target audience.

Who did you write this for? Did you have some target users on board right from the start? Did you pre-alpha launch with some people actually using it? Or did you implement everything and then try to market it?

It feels ... undirected.

Added in edit ...*

I've read more of your other comments. It seems that you are targeting early-stage programmers. Do you think HN will be a source of users?

If you want customers, you have to go to where the customers will be. To do that you need to decide who your customers are.