A basic web app like other posters are describing is just some html+css (admittedly are awful) then javascript and local storage.
What that kind of a stack enables is potential. So you're happy with your app. Take what you already know, learn about a server and a client and make a scoreboard. Now you understand client/server you can make it collaborative. etc.
Yeah. I was making simple choose-your-own adventure stuff in grade 6 or 7 with just HTML+Javascript. There was no stack involved, just me experimenting with copy-pasting stuff I'd seen on the web.
jQuery makes even that learning curve a lot easier (e.g. $('.text-box').text() instead of whatever even hackier stuff I was using back then).
What that kind of a stack enables is potential. So you're happy with your app. Take what you already know, learn about a server and a client and make a scoreboard. Now you understand client/server you can make it collaborative. etc.