What's this? theory?

Am i sleeping or is this a theory or something? I have no recollection of a game like that.

What's this, where did i go wrong?

3...exf4? is already a mistake. 3...d5 is the only viable move.

chess.com has no lesson with the word "vienna".. duh

It's funny i ended up in Levy's channel again..

His first words grabbed my attention; "It's pretty rare in a game of chess to be able to surprise your opponent as early as the second move, but that's what this video is all about.. vienna system and the vienna gambit"

This sentence is perfectly describing what happened to me never thought i'd find myself into deep sheet of trouble by the 3rd move.. I played 3. exf4 before.. but this.. is.. new.

Isn't 3. ... d5 better than taking on f4?

I didn't know anything about Vienna system & gambit till today. That's why the title is 'theory?'

I watched some lessons after this and i now know d5 is the best response. But even Levy is commenting d5 move like that "if you see d5 that means your opponent knows the theory" It's not something you can differ immidiately.. especially on the move 3.. 

There are some lines in Levy's video, he says if you see this responses at this point, either your opponent is cheating or they are anonnymous GM you are playing.. Or pure luck..

This Vienna system is huge thing to study.

The Vienna Gambit is one of those few gambits where you should NEVER accept it no matter how good you are.

Probably this is the critical line:

Not that dangerous for black probably