Thank you! I've cursed Mr.Loud many times for the constraints of his competition, but in reality I enjoyed every minute of the challenge ;)
This is my first and it worked really well for me. Before I didn't feel that I had the right skills (ie I thought that you 'have to know the tricks'), but then in the day job and hobby programming I like to be efficient (with 8-bit computers you have to be!)
Yes, I saw the invaders in a tweet - brilliant!