I played a very early build of Minecraft, when Notch posted it to an IRC channel I frequented at the time. It had primitive but recognizable voxel graphics, and almost no features. But the basic principles of exploration and building were there.

I can tell you with certainty that very early and unpolished prototypes of Minecraft were fun, and that the potential was obvious. (Though of course no one could predict just how huge Minecraft became.)

That's completely false and grossly overlooks what makes games fun in the first place.

Prototypes are your absolute best indicators to determine if a project is worth investing into to reach completion or not. Because you find your fun factor at the prototype level.

You'll get at most better visuals, sounds and more balance in the game with polish. If your mechanics aren't fun to begin with, polishing them will do absolutely no good.

> I doubt you'd have something as fun as the hit title.

I doubt it too.

> Prototypes are not good indicators that something could be fun.

This is what I disagree with. The prototype won't be as fun as the final product (because otherwise, why bother polishing in the first place?).

Take Infiniminer, an obvious source of inspiration for Notch. It's only got the very minimum of features; it's kind of a Minecraft prototype. It's also got the features that originally got me into Minecraft: building arbitrary structures in a large virtual environment. Minecraft is better fleshed out, of course, but the core of the game is there.

There's going to be a point where you've got the irreducible kernel of a game concept. That is the prototype. Remove items, crafting, mobs, infinite world sizes, lighting, and textures from Minecraft, and you've still got the kernel: a virtual building kit. It's an awesome idea, fun on its own, and expandable into a "real" game with goals, achievements, etc. It's a great indicator that a fleshed-out version of the game may be fun.

Now, you can't build something smaller than a kernel of the concept, call it the prototype, and make a judgement based on that.

Minecraft WAS infiniminer

At the beginning, yes. The beginning alpha/demo version was. Infiniminer was like the prototype, and the demo was like the engine reimplementation when it was at the same level of development, when the previous dev team quit and deleted the original source tree (not literally true; I'm speaking figuratively).

It was a clone with aspirations of becoming something greater.

I think at some point you have to use your imagination and intuition to fill in the gaps. This is something you have to do at many stages of the process anyway right? A prototype let's you confirm that your basic ideas are sound and you can focus on imagining the other aspects that bring it all together.