Cheers Spitfire.
I got the idea from a Teletext advent calendar in the 1990's - for those who might not know what it was, Teletext was like a very early version of the internet, as it displayed all sorts of news and information on your TV using very simple 8 bit graphics.
One year there was a Teletext Advent Calendar: The first day had a completely black screen, but pressing the "Reveal" button brought up one element of the full picture, probably an elf or a present or something.
Day two had day one's image already displayed, with a second part visible when the "Reveal" button was pressed.
This continued until Christmas Day - I think the final picture was of an accident at the toy factory at the North Pole, but I can't find any pictures of it
