basically it’s like this
(credit to armor gaming)
how it works: you will have a random selection of stages (missions, whatever) into this much percentage:
chicken invasion: 80%
boss rush: 10%
darkness, asteroids, comets, any other stage: 10% (excluding key rushes, and droids)
it will go for 140 missions (0 to 140%)
the items you have will stay forever, it cannot be added (like if you have 2 lives, you will stay 2 lives the entire time)
this resets weekly, or monthly