Thanks so much for the mention. It's indeed a lot of work, but we've done so much with such a small team and it's only accelerating as we layer all of our solutions on top of each other. We're solving one problem at a time with focus on patterns and abstractions that makes it easily extensible and could support virtually any language.

With the Universal Package Manager (https://github.com/replit/upm) we're trying to encode the best practices in package management behind a single easy-to-use interface. One of the most fun features is that you can `import` or `require` a package and we'll just guess what you want to do, install the dependencies for you, generate a spec and lock file.

With prybar (https://github.com/replit/prybar) we're trying to create a universal interactive programming experience that behaves roughly the same for every language.

And, to be open-sourced soon, our window-tiling manager and workspace (https://repl.it/blog/ide), we're trying to build a framework that makes it so easy to build complex, plugin-based environments, such as IDEs, very easy to build.

We also leverage a lot of awesome open-source projects and standards, like the Language Server Protocol by VSCode/Microsoft, that abstract over language features and makes it easy to provide an amazing experience across languages.

Edit: if it's been a few months since you tried Repl.it, give it another try, we've made a lot of progress since then. Multiplayer is now out of beta, we have Git integration, and we've done a lot to make it faster and more reliable.