In it, you can do really well if the enemy doesn't get to your base even once. However, even if they do, it's not game over. But you do miss out on an extra reward.
And it's interesting, because I realised the inner conflict involved - do you just start over as soon as one has touched your based? Given all the effort you put in AND it doesn't mean you lose outright?
So what drives you to repeat play? Wanting to get through without having to live with having made that choice. To get through absolutely clear of any enemy getting to your base. PLUS, as with alot of games, it just seems possible if you do a few things different.