I've played both of the games. Where's part 3? Off of the top
of my head, one feature to add is to have a "continue from last
checkpoint" option, but have two of them. One for when playing
solo, and the other for a co-op game, but allow the player
to select levels completed in the co-op game. Also, in the
selection of either "continue" function, list where the game
was left at.

One thing that I think that I liked better about the first one
was the simpler graphics. It could have been how I was sitting,
but it seemed like I spent more time trying to figure out where on
a map I should go. Of course, I was tired. That may be
why I was lost (sort of).