Really impressive work for just one week time! Always hard to come up with some challenging puzzles that are neither too hard nor too easy - but you managed it pretty well! I like the gradual introduction of new game mechanics and the sense for little details - like making the volume of the landing sfx dependent on the falling height. While playing I thought about three improvements I would consider:
1) It should be visually more obvious which of the two characters you are currently controlling. Right now the only difference is their different color which is sometimes hard to notice.
2) One character has the special ability to switch gravity - why not add a special ability to the other character as well? Or did I miss something?
3) Instead of switching between characters automatically I would make the player choose for himself, which character he/she wants to control. Right now it seems like I always have to play with the red character again, once I failed with the green one - sometimes I wished for just having another try with the green one instead.
Congratulations for handing in such a polished submission! I really hope you're going to develop this entry to a fully fledged game because it has every potential! :)