You can just analyze the graphical output of the browser and hence make your hack useless. The underlying problem of this game is just too easy to solve.
@readerrrr: I'm commenting here because HN doesn't let me comment your comment.
> You can always make the game itself harder on top of all the anti-bot tricks.
You are implying two things here. Firstly, that its' always possible to make the game harder and, secondly, that anti-bot tricks can solve this issue.
I'm skeptical about the first part and strongly disagree with the second.
In regard to the first part I'd say that it's hard to make the game harder without making it unenjoyably to play. How'd you integrate a sufficient amount of complexity into this game without ruining the fun? That it's in principle possible shows Go. Interesting problem.
In regard to the second part I say that it's just adding (futile) noise and not tackling the fundamental problem. The player has to see at least the map. He then draws a graph in a program that produces a function that has nearly that graph and gives a string defining that function. The user just copy and pastes it into the game.
You can always make the game itself harder on top of all the anti-bot tricks.
The game has to be only hard and expensive enough to hack so that the effort isn't worth the result.
Of course with unlimited resources you can pretty much solve anything, if you assume those, then everything is easy to solve. But assuming that is simply ignorant.