Finally figured out how you'll finish up a planet. I was just gonna have it announce that you were dead once your health hit zero, but I never much liked that. If you're not paying attention to your health, it feels that the game pops up a dialog announcing that you're dead at arbitrary times.
My new rule is that you can only attack hexes if you've got the strength to do it. If you try to attack a hex without the firepower or strength, it won't let you do it. So eventually you'll end up in a place where you just can't go anywhere. You're stuck and you need to get off the planet.
Now then, there is an escape pod. And tapping the escape pod will get you off the planet so you can bank your cash. But it's not free. I gotta think up some kind of "Deal or No Deal" algorithm that the pod will live by. If you've got plenty of remaining opportunity to make money, the escape pod is cheap. If you're boxed in by giant monsters and have nowhere to go, it'll cost quite a bit more of your winnings to escape.