I don't even think he should get credit for a good first 30 minutes. As any writer knows, the first 30 minutes of a movie are the easiest to write. Especially a movie like this. You just make crazy stuff happen so everybody goes, "whoa, what's going on here?" It's actually creating an interesting story after that crazy stuff happens and then explaining, in a satisfyiing way, why it happened, that's the hard part. That's where writers earn their salary.