you people are looking into wrong place. Just because it's a "game" doesn't actually make it into a game. you're hacking a website, not a game. it's completely different thing.
browser "games" are flash based (at least most of them) and you need flash decompiler / debugger to be able to make sense of them. sending packets and other stuff is worthless. like i said, you're hacking a website, not a game.
websites have a lot higher security than game protocols. there are no tutorials, because it's impossible to make a tutorial for something like that. you'd have to learn how websites work from the scratch. you have to learn what is SQL injection, CSS (cross site scripting) ..etc.
then you need to put all that together and see if you can find a vulnerability in the website, if you find one, then exploit it.
always test by disconnect your internet and see how much of the game you can play, if it instantly gives error, then most stuff is server sided, if you can finish whatever part you're in, then most likely you can hack it with some flash debugger or memory tools and change anything within that part and changes should be recorded.