This was pretty good! I liked the idea of switching between different gravities, though the cooldowns made it less fun. Also, the fact that the moon and Jupiter is used in combination made the fact that they don't have equal cooldowns pretty annoying.
There were a few bugs (as expected in a game jam); the ones that were particularly annoying were that you can't jump if you're too close to a wall (or even a rat), and that the moon gravity sometimes didn't work (as in, the cooldown starts, but I'm still jumping normally).
I really like the idea of combining gravities as well; coming up with a good benefit of using higher gravity was quite clever! Though Earth gravity seems to be pointless, since that's what you're at when the others are on cooldown anyway. Maybe only being able to have one active at a time (but they last until switched) would be a good way of solving a few of these concerns I came across.
Anyway, it was pretty fun, so well done!