I've applied and we had the first interview by phone. The next step would be a technical test. The recruiter ghosted me and I never got to the test. After 20~ days, I sent an e-mail asking for an answer, even if negative. Never got a reply.
100% agree with all of you in this. I was once rejected for "taking too long to dive into coding." I was only given 20 minutes to solve an algorithm, and was clarifying input and output, edge cases, and pseudocoding before implementing.
I would expect charging for storage. Let the user try whatever he wants for free -- both the mobile app and the website, but after some point, say one month of average usage, one faces a limited storage problem, solvable with an account upgrade.
You can use any language, but it's not like they are all equal and have the same tooling available. Rust has some distinct features and there is a natural lack of resources as the language is still new, so it's interesting from a developers perspective that someone went through the work of doing all that from scratch and made it to the end.
Also it's an alternative to C++ which is heavily used in gamedev. I personally believe Rust can shine in gamedev and every experiment is interesting.