Seems very fun but the instructions are really unclear.

There's no indication of the class having to be defined in the scope (though it makes sense). The password isn't really clear on being in the filesystem (at first I assumed it's in the actual github repository for the game) and "no __builtins__" sounds more like you can't use the literal string "__builtins__".

I feel like it would've been so much more fun if you could see how the rules are checked instead of having to figure it out.