Nicely done!  Great idea to use a square....I have a jig and it is almost the same....slightly less on one side and slightly more on the other, to form a perfect 90.  You just have to remember to use one of each side on the cuts!  DAMHIKT   
I mark each side of the jig A and B, then do the same on the pieces I've cut.  You just have to watch that you have one of each, A an B on each corner....and trust me, it is easy to get them mixed up with some sort of method like this.

Mike