Minecraft has sold over 625,000 copies, despite still technically being in its Alpha phase—which makes sense, really, because Minecraft is very much a game about discovery and possibility, a game about imagining what might be hidden around the next corner, or through the next cavern, or for that matter, in the next update. Half the fun lies in speculating about what the game could be. It could be a sprawling player-versus-player siege engine, or a community construction project, or an MMO that goes on indefinitely without ever asking you to grind your stats. By balancing elements of survival and exploration with a robust system of crafting and building, Minecraft has positioned itself somewhere between the original Legend of Zelda and an unimaginably large tub of Legos.

For those of you who haven’t tried Minecraft, the game’s world is notable for two major reasons. First, the whole thing is randomly generated, and so large as to be effectually infinite. As Douglas Adams once observed, something exceedingly large—eight times the size of the Earth, in the case of a Minecraft world—can actually seem bigger than infinity itself. Look up at the stars, and the image can be, in Adams’ words, “flat and boring.” Walk around in Minecraft, and you feel like you could walk on and on forever.

The second, arguably more important feature of Minecraft’s world is that the entire map can be torn down and rebuilt, piece by piece. The game-world is composed of 16x16x16-pixel cubes and, with a few notable exceptions, each of these cubes can be broken down into its constituent parts; trees become logs, which become wood, which becomes sticks, and so forth.

This is where the survival element comes in: As your explore and build, day turns to night, and the world becomes flooded with monsters. In only a few in-game days and nights, you can build yourself a mud hut, and a suit of leather armor, and some tools and weapons—and that’s enough to survive, since you don’t have to eat except to restore your health, and you won’t lose health while reclining comfortably in your unambitious little hole in the ground.

But if you want your mud hut to become a stone tower, and if you want your leather armor and stone tools to be replaced by nigh-indestructible diamond bling, then you’re going to have to branch out, explore, take stupid risks, get lost, get burned to death by a lava flow, get mobbed by spiders and skeletons and zombies and these bastards.

That’s the magic of Minecraft. If survival were really the point, then you’d have beaten the game as soon as you finished your stupid little hut. Thus the point is not survival or accumulation, but possibly. The point is to imagine what the game can do, and then go out and bloody do it. You can build a replica of the USS Enterprise. You can build a working computer inside the game. And most tantalizing of all, you can dream of what else you’ll be able to do by the time the game is finished.

So here’s the thing about buying Minecraft while it’s still in Alpha: You’ll be participating in these heady days of seemingly-infinite possibility, and at the same time, you’ll be helping to push the game along into its ultimate iteration—toward producing even more concrete, fully-realized possibilities.

That, in my humble option, is pretty good for about 12 bucks—and more than half a million of my fellow gamers seem to agree.