Also, I'm not sure if converting between 5 digit numbers and words is a good starting task, unless you want to dive right in with German's (in)famous word chaining ability.

Quick feedback: the website looks very polished and intuitive. I especially liked the test about articles, where I didn’t have to type. I liked that the website works well on mobile too. The content is not what I’d call games though; based on the name I expected something different than test questions and quizzes.

Some German natives may argue that the time short forms are wrong as they prefer "dreiviertel" instead of "viertel vor".

So the Sims, I'd guess, is probably a good example for building vocabulary. Edit: example https://dasboudicca.substack.com/p/i-learned-german-and-siml... (This writer has lots of game learning reviews)

It's a bit similar to Grammatisch, although that just focuses on the grammar.