All of this is a good example of what not to do.
Don't let your parents rule your internet life. I never told my parents what I do my computer because they freak out at the thought of me even having friends. [My mom is crazy, she thinks everyone is a rapist/out to get me LOL.] Not to mention she's very religious, she would throw certain toys away because they were "demonic".
Next time try not to tell your parents what you do on the internet or anything. I never tell them what sites i go on, what games i play, etc etc. I know they're concerned, but I feel like they're overprotective lol.
When your parents aren't looking, play FeralHeart. When they come around, minimize/close it. If they check your files, try hiding it somewhere very unlikely that they wouldn't really look where it is.
I know being "sneaky" is wrong, but hey, sometimes you just have to "do the wrong thing" when it comes to this kind of situation.. I never tried 'convincing' my mom to do anything for me. It was just a "No" and a "because i said so" so lying is usually my only choice. I sure hope you can play FH again, good luck.