Here's one way to use nested rules in Kodu. In this example, rules 3 and 4 won't run unless rule 2 is true. What we're doing here is using score to keep track of ammo. When the user presses the trigger, we check the score. If it's above...
Want to know how to get those cool little pictures in your level description? Just type something like this: "Look out for the falling <apple>! Press <A> to jump and <LS> to move!" Here, apple would be replaced with a picture...