I played through the game in single-player and found it a blast. Not much grinding was required since the pace of leveling up is fairly consistent across the full game and any experience earned on a stage where you lose all of your lives is kept, but it does take effort to earn enough cash to afford the more expensive items in the store.
Beat the game last night alone and I had a great time. I also leveled Scott up to the max level and maxed out his stats. I'm playing through again tonight or tomorrow to beat the game on the hardest mode. Then I plan on beating the game with all the other characters. Sure I might get a friend to play along sometime this weekend but I'm having a great time playing this alone also.
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