difficulty of game: I agree; Oddworld (puzzle) games have to be challenging enough. So I too hope that the next game will be more difficult, so you actually need to use your brain on how to solve things, and need to explore to find secrets. (Also think about the 1 hit kills discussion)
Length of game: disagree; In my opinion the game doesn't have to be longer. Longer is fine. The more the better off course. But it only takes more time to make an extra long game. Decent multiple endings can make up for that. I prefer a higher replay value.
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