"People are asking, what the game is all about, what do you do," says Hello Games' Sean Murray.

He perches on the edge of a leather chair, leaning into a TV screen where No Man's Sky's unmistakable hues are glowing. He is about to demo the game to me.

"Yes," I reply. "They are."

I've been wanting to play this game for a long time. I'm excited and I'm curious, but I'm also aware that this is a game that has revealed very little of itself to the world.

By virtue of appearing to be something that is highly original, from a developer that is outside the mainstream, No Man's Sky has accrued a following, as well as expectations. Since its first appearance back in 2013, it has presented itself as an entire universe of possibilities, an endless array of worlds, waiting to be discovered and explored by you.

This is its second E3. We have no solid release date, though 2015 remains a possibility. It's been signed by Sony and offered up as a key component of that platform's attraction.

The time has come to begin fulfilling expectations. Murray begins the short demo of No Man's Sky.

30 minutes later I have a clearer picture of what this game actually does. Taken by its individual parts, it's nothing particularly outlandish. It's a space-exploration game with heavy resource-gathering elements. But taken as a sum of its parts, it's a game that demands attention and, still, expectation.

You are in first person, wandering around an alien landscape. There are creatures. One of them is hostile. It looks like an angry, slightly deformed goat. It won't leave you alone. You have things to do, places to be. You shoot it.

A marker on your UI tells you that your heat has increased, that hostile forces are likely to be looking for you. Sure enough, alien robots appear on the horizon. You run around for a bit and you shoot them. More alien forces arrive, bigger robots. These are the Sentinels, a race of self-replicating warriors who provide combat and peril.

It's time to leave. You head for your space ship, nestled among the undergrowth. It takes you away, fast, low over the landscape, and then high, away into space. This is nice.

No Man's Sky's publicity campaign has been a matter of strict drip-drip, with small slivers shown from time to time, usually accompanied by bold claims. It is a game that has now reached that point where those who are interested demand greater access to the game's fundamental point, in order to sustain their interest.

This E3 is crucial for the people at Hello Games. They have meetings booked throughout the show, a different media outlet every half hour. This is not a game that can, or should, be fully appreciated in the time it takes to watch a sitcom. But it's better than a highly scripted conference "reveal."

Murray is playing the game freely. Stuff is happening at random. The goat-like creature attack wasn't really supposed to happen, but then this is a game in which the unexpected is part of the fun. You are exploring alien planets. Weird events ought to be part of the landscape.

So now you are flying in a spaceship, around a space station. You dock and look around. We don't have time to stay, but this is a highly populated area, a place to trade and to buy new ships. In No Man's Sky, part of the progression plan is to get richer, to buy a bigger, better ship, that can help you get richer and go further.

As in many space-trading games, you can choose your own path. You can be a warrior, a pirate, a trader, an explorer. In order to do these things though, you need to gather resources. these can be won in space-combat (we don't play any space-combat) or it can be won by exploring and gathering.

We head towards another planet. Your ship has different speed-settings, to account for the vastness of space.

This place is far less lush than the last, more rocky and jagged, like an unpopular beach. There are more creatures, a bit like the ones on the other planet, though slightly different.

Scattered around are red and blue crystal shards. You shoot them. They disintegrate and a counter on your UI ticks up. These are chemical resources that can be mined to craft more valuable chemical resources, that can be used to trade and sell. Murray says that these crystals are commonplace. Intrepid explorers will find more precious crystals that yield rare booty.

You have a jet-pack so you jump up into the air, and then down into the ocean. Your suit allows you to walk underwater. Your suit, jetpack and weapons are all upgradeable, as your wealth increases, and as the scope of your discoveries widen.

Under the sea, there are fish swimming about. Something is shining on the seabed. A box. You pick it up. It yields a specific benefit, an upgrade to equipment. These loot drops are scattered throughout No Man's Sky. Obviously, the game wants you to explore its many worlds.

Murray shows me the inventory system, which covers all the usual things: vehicle, weapons, equipment, trading goods and so on. Better ships have bigger inventory bays. This is important. There is not much benefit of spending this game in the very first crappy ship you are given.

Back on land, you perform a scan. Great vertical shafts of light signify what Murray calls "points of interest." We don't have time to explore them, but they include a beacon from which new discoveries can be transmitted and rewards gained.

I ask Murray how other players figure in this game. He says it's not an MMO. You might see other players on the surface of planets, and you may be able to interact with them on a basic level, but there will be no combat or trading. "It's a bit like Journey," he explains.

You're probably getting the picture by now, that, gameplay-wise, No Man's Sky is not wholly unfamiliar. You are tasked with exploration, discovery, resource gathering, combat and progression.

So far, we have been told that there is an entire universe at our disposal. Of course, if that universe boils down to half a dozen planets that look sorta the same, and various configurations of angry robots, No Man's Sky is unlikely to fulfill its great promise.

But it still holds out an expectation of adventure, of the unexpected, of delight. Although the mechanics of the game are familiar, they also seem solid. In the area we explore during this demo, there is plenty to do and plenty to see. I feel a yearning to make myself powerful, to go in search of new places, to forge my own path.

Next time I look at this game, I hope to play it for a few hours and, perhaps, a few days. No Man's Sky isn't so much a mystery any more, but it remains something to value.