So, after 2 hours of developement the news :

1) theme suck, a lot, it’s just a restriction, not a theme !

2) already 5 cups of coffee has been drink ^^

3) I’m not proud of my idea, I’m going to do a simple space invaders clone… With snowmens ^^

The first screen :

This is the first shoot, I didn’t draw the snowmens’ sprite already, so I use an old sprite for the moment.