Most videogames these days pack some sort of post-ending content, whether that be additional levels, tougher difficulty settings or collectible objects you didn’t pick up the first time through.

The more punctilious game reviews give these bonus options a grade under the heading “replay value.” The extras are usually extraneous, though — little rewards for truly devoted fans who want to keep playing in the game’s world. Everybody knows the good stuff is all before the ending.

Not so in Super Mario Galaxy 2 , the stunning new sequel to the imaginative 3-D platformer that first launched Nintendo’s plumber into space. In fact, the Wii game trots out its most complex and creative challenges after the final credits roll.

If you haven’t seen them, you haven’t truly finished the game.

(Spoiler alert: Details about Super Mario Galaxy 2 follow.)

As you complete levels in Super Mario Galaxy 2 , you add to your collection of Power Stars. With only 70 stars, Mario can complete his perennial task of saving the Princess from the Koopa king. But after this, there are another 50 stars to collect, both by doubling back and finding more stars in previous levels — and by entering the secret World S that opens up after the credits.

Picking up the rest of the stars isn’t just a matter of looking for hiding places in levels you’ve already played. Each Power Star is a reward for completing a distinct level of the game. Sometimes these are unique spins on a previous level, but often they are totally discrete challenges.

Super Mario Galaxy 2 is a game packed full of surprises — each level is different than the last, with some unique twist on the simple mechanics that will feel brand new even to people who played the hell out of the original. You might be forgiven for thinking that those surprises might slow down toward the end, but they don’t. In fact, the game doesn’t let up for a second — right up until you collect the 120th Power Star you’re constantly being asked to do new, different things.

There’s a new design choice in Galaxy 2 that adds another layer onto the challenge of finding all the stars. In the first world of each level, there’s a Comet Medal hidden somewhere. To cause Prankster Comets, and thus more levels, to appear, you have to find these medals inside the levels before you finish them. If you don’t grab one the first time, you have to get it and complete the level again. This adds an interesting twist, since you’re constantly trying to complete this secondary objective so you don’t have to do the level over.

Appropriately enough, the levels you unlock by collecting medals are some of the hardest in the game. Some might send you back into a tough level and ask you to finish it without taking a single hit. Others might place a hundred purple coins in a level and task you with collecting most or all of them within a time limit.

These, too, aren’t just busywork — it’s not as if the purple-coin levels are forcing you to traipse over every square inch of a level in the name of reusing assets. These are testing your ability to perform perfectly — to get Mario to go exactly where you need him to be. Previous levels give you lots of fudge factor; the comet challenges require perfection. This is a lot less onerous than it sounds because Galaxy 2 ‘s controls are so perfect.

A Whole New World(s)

New twists on old levels are all well and good, but the back half of the game is also full of brand new experiences. One of my favorites is a level built entirely around the “bowling” mechanic that the game introduces for one brief instant in the first level in which Rock Mario appears. This moment at first appears to be a throwaway joke, but hours and hours later it turns into a challenging level in its own right.

Another galaxy is made up of boss encounters from the first Galaxy , strung together in one lengthy gauntlet. And the last level of them all uses walls that only appear when you spin in the air, meaning that you have to wall-jump over a gaping bottomless pit, spinning to turn the walls on and off.

Most of these concepts are used exactly once in the game. Many game designers would use them over and over until they became boring, but the Mario team gives us one perfect version of the concept, then moves on to something else.

Super Mario Galaxy 2 does have lots of that more traditional sort of post-game bonus content. Once you get 120 stars, three Green Stars are dumped into each level. These are quite different from the Power Stars — they aren’t markers of a completed level, they are collectible objects scattered hither and yon in hard-to-reach or hard-to-see places.

This, I’m going to skip. The Green Star gameplay incorporates some elements I don’t really like about adventure games — pixel-hunting and collect-a-thons. So for me, the allure isn’t there.

Apparently, there’s one final master-class level that you can play after collecting all 120 Green Stars. No thanks. I mean, I’d love to play it, but I don’t see myself doing the work it would take to get there. I have little desire to putter around in levels I’ve already played. Yes, the Green Stars are well-executed bonus content, but it’s still clearly bonus content — not the main game.

Just don’t make the mistake of thinking that everything following the credits is bonus content. If you stop after the first 120 Power Stars, I won’t blame you. But if you stop before that mark, you haven’t really finished Galaxy 2 .

Images courtesy Nintendo

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