Its calculated by human .Me!
not all the parts calculated of course:
the frog space ship
the "tails"
i didnt knew what weakest then wall

I think that it will be nice from me that i give a three line tutorial so:

1)make a fuse
2)make somthing that will continualy make the fuse at the same speed as the fuse "burnage" (the hardest part)
3)Remember: there weak ruls and strong rules so if two rules need to burn in one px the strongest wins
i know that it cant help to much so: sorry.