I always love coop game like this so I gave this game a try.
That being said, I feel like the game is kinda crude in level design. Some early levels are completable but some requires rough tactic which may not be known to most players.
My suggestions are :
1. Make early levels as tutorial levels with no holes and no traps to teach Mort's and Phil's abilities.
2. Add sign near exit to tell player that is the end goal.
I'm currently stuck in level 6 in which I couldn't bring Phil up because Mort has dropped to ground floor to open the door for Phil.