Yeah that's basically it! The "parameter t" is actually just "set variable t to the first parameter (denoted by .0), and {f0:...}. just creates a function with one parameter that has a default value of 0.
I'm really surprised how much you got from this haha!
The final branch of the if statement, the "Oi" means print(i). O is the print command i think.
Still, super impressive that you could figure this out! i cheated by simply watching JJ design the language on discord lol