I'm tremendously jealous of whoever got to write it. To get paid for (probably) months or years to work on something of this technical sophistication, with (I guess) virtually unlimited resources and access to technical details us mere mortals would never get their hands on; it's an awesome project to hack on. It's really a clashing if raw mind power - pulling out everything you have, with great resources behind you, to beat the defenders who are doing everything they can to stop you.