Very important! Not forget to save! The game does not create automatic Scores or can be started at any level again. If you have no Save and builds on the 5th mission or so crap, you must still have a go from the front, if you want to correct it. Is for me but not a lack, because you can saven anytime. I have got used to store every time after discontinuation of the troops.
Otherwise, I can only say: save a lot of fun earth! -D