Stolen idea?
This isn't even the only game ON THE FRONT PAGE OF NEW GROUNDS that uses this idea of an big world map that you unlock by finding upgrades to accesses new places. Off the top of my head I can count 6 or 7 (edit: oh wait remembered another 2 maybe even 3! so new total of 9 or 10 games) that use this idea. True it must have started somewhere but it's clearly a new style of platformer that we all seem to like and artist like to create. Yet slatting this game for being a rip off of one or another at this point is just redundant and petty.
If you want to talk about the game not adding anything new to this type of game? Go ahead because it does not. The game has no new ideas that I've come across yet but the art style is wonderful and the platforming is smooth enough and challenging in places with out being stupid. In other words it a nicely refined game of this type it does not innovate and it's clearly not the best of it's kind but it's kept me playing and I've enjoyed it a lot so far. The seems to be no real story so far which is a downside as it means the endings, when I get to them, will be no where near as good as they might.
In other words this is a booming new game type that has come up a lot over the last year or so. To complain about it being ripped off is to complain that ever tower defence game stole it's ideas or any other of the countless game types that game makers use as a frame work. Every game will rip off ideas when building it's frame work as that is how design works, nothing is every fully original. There a many reasons for that and no time to get in to them here. Still the point remains that this kind of game has become an established game type and the only way to judge them is to judge how well they do it and if they offer anything new to that game type.
Personally this seems to be at the more shallow and simple end, if you want to see this game type at it's best you may want to check out "endeavor" which you can find right here at newgrounds and was on the front page a few weeks ago. It's vastly better in almost every way... but that does not make this game bad!
Understand now? good.