[In this in-depth critique, game designer David Sirlin (Super Street Fighter II Turbo HD Remix) analyzes Nintendo's Super Mario Galaxy, discussing what it did right - and what it could do better - in creating its 'polished, beautiful' game world. Please note that this article contains some gameplay-related spoilers for the game.]

I've only said "Wow!" a few times in the last couple decades of playing games. One of those times was for the breakthrough Super Mario 64, a game that took action/platforming into a 3D world and made it work. It's fitting that I said it again over its (true) sequel, Super Mario Galaxy, a game that took action/platforming even more into 3D and made that work, too.

In point of fact, I might have more reason than most to say "Wow" over this game. Years ago, I worked at a small company that went out of business where I was designing a 3D platform game that played with gravity. Now, so much later, it's great to see Mario Galaxy realizing these same ideas in the most clever, polished, beautiful ways possible.

Why is Mario Galaxy so good and what can we learn from it? To borrow some terms from Nicole Lazzaro's four kinds of fun, Mario Galaxy has hard fun, easy fun, and social fun as well as the ability to evoke the emotions of surprise and wonder.

Hard Fun

Gamers know this kind of fun all too well. This is the fun of overcoming obstacles and attaining goals. When you succeed at an especially difficult challenge, the Italian word fiero describes the emotion you feel as you raise your fist into the air triumphantly. Mario Galaxy has 120 stars to collect, offering plenty of this type of fun.

Hard fun is so common in games that the only thing worth noting here is how well Mario Galaxy informs the player about exactly which goal he's going for, which goals are completed, and how many goals are left. I think this clarity magnifies the fiero aspect of the game. Putting the tally of hard fun at center stage (the number of Mario Stars, out of 120, you've collected) makes it all the more satisfying to achieve the goals.

Easy Fun

Ironically, this fun is much more rare in games. This is fun that's not bound up with winning or goals. The entire Nintendo Wii system has an advantage here because the motion-sensing Wiimote lends itself to easy fun.

Collecting the star bits (the colorful, glowing ammunition that bounces around everywhere) with the Wiimote's pointer is easy fun. Shooting the star bits at enemies is easy fun, though hardly ever required to achieve goals. Using the left-right-left-right gesture to do the spin attack is easy fun.

Another part of easy fun is exploration and variety. Some of the gameplay variety in Mario Galaxy includes:

• Flying with the bee suit
• Shooting fireballs with the fire suit
• Creating frozen platforms and ice skating with the ice suit
• Becoming a ghost who can turn invisible and float with the ghost suit
• Jumping very high with the spring suit
• Riding a manta ray on the water in a race
• Riding a turtle shell underwater in many situations, including races
• Balancing on a ball as you navigate through a level
• Flying with the red star suit
• Numerous tricks of gravity that vary across several levels

Just the moment-to-moment interactions involved with these things are fun, without even considering how they are used in the context of hard-fun-goals.