Just finished single player and about 1/2 of co-op and noticed I hadn't come across a single level with one of those suction tubes.
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Overall I'm pretty disappointed. Story was great, but it's really hard to overlook how short it was when that's all there is to the game. No leaderboards, no challenge mode, and no modding support.
Also, I really can't believe they added an item shop for this game at release. Co-op is fun and all, but there's not too much of a reason to go through it more than once right now.