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.

I'll test it more, congratulations.

One mistake I found though: in the clock game the game's solution for one o'clock times is "eins", like "eins Uhr dreissig" for 1:30am/pm. That's not correct, you'd use "ein" instead of "eins", so the correct solution would be "ein Uhr dreissig"

Keep up learning german, I know from non-german coworkers how hard the language can be to get a grasp on!

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