I haven’t played Minecraft, but I’m terribly addicted to Minetest, an open-source clone of it. What is it that makes the game so captivating?
When I start a fresh game, there’s a carefully graduated slow exponential increase in the character’s power. At first they can only dig dirt, break trees with their hands, and transplant plants; once they’ve acquired some wood to make a wooden pickaxe, they can mine stone and make a stone pickaxe, which allows them to mine stone more quickly, and then a stone axe, which allows them to chop trees more quickly; and some coal, which allows them to make torches, which makes it practical to mine underground and in caves, which makes it far easier to find coal and then metals; and so on. The sequence varies a bit depending on what environment your character finds themself in. I had a world where I had to travel a long way to find any wood, for example, and where I never did find any roses, which are necessary to make a bed. In the world I’m currently playing, it took me a long time to find a jungle, which is where you find the jungle grass you can convert into cotton seeds in order to start farming cotton, also necessary for beds.
There’s a certain balance needed between surface farming and deep mining. There’s a progression of tool types — wood to stone to steel to bronze to crystals (diamonds and the softly glowing mese crystals) — which roughly corresponds to how deep you need to go to find the necessary materials. But to dig deep quickly you need ladders, and ladders require lots of wood, which can only be obtained on the surface. (Mina likes playing with mods that add monsters, make ladders cheaper, and add hunger, which also generally requires that you go to the surface to satisfy it.) At different points in the game, different resources are the limiting resource for whatever you want to do, and you can play for many hours before you run out of things in the world that surprise you.
And, in the mining process itself, you’re always looking for something that’s fairly rare, and you will run across its random occurrences at a frequency proportional to how hard you look. At the surface, even coal may require searching for quite a while, and iron is not found at all. Later, once you have iron tools, you can easily dig down far enough that you can find more coal and iron than you need, but if you know bronze tools are better, it takes a while to find enough copper. And once you’re deep enough to find enough diamond and mese that you don’t need to use metal tools any more, it can still take a lot of searching to find each new crystal deposit, and you’re frequently in danger of stumbling into lava. This proportional variable reward mechanic means that, in addition to the overall macroscopic reward schedule for continuing to play, you have a microscopic reward schedule where you know that the very next stone you punch with your pick could have diamonds or mese crystals behind it, making the whole journey down from the surface worthwhile. This makes it easy to keep playing for just one minute more. In fact, it makes it easy to forget to eat in real life. Or sleep. Or go to class. Or go to work.
All this is to say that the reward schedule is well calibrated, somewhat randomized, and robust to player strategy. But I think there’s another reason as well.
My apartment is three meters wide, 2.6 meters tall, and thirteen meters long. At one end, it has a glass window, which is about two meters square. The walls, ceilings, and floors are white, and there is a bit of a recess around the edges of the ceiling. I pay US$300 a month to live here, despite the inconstant and often uncomfortable temperature and troublesome noises, especially on weekend nights.
I just constructed a sort of replica in Minetest, in a world where I had already been playing and thus already had crystal tools, about 40 meters underground rather than in the sunlight. Replicating my real-world living space as described above took me 33 minutes; although that doesn’t include the time to cultivate, harvest, and mine the wood, diamond, sand and coal consumed in the process, I think the direct labor on the building was the bulk of it. Merely digging out a 13×3×3 space out of gray rock would have been much quicker, less than five minutes, but I made the extra effort to reduce the ceiling height from the usual 3 meters to 2.5, adding the glass window at the end with a light source behind it, and making the walls, ceiling, and floor white with a sandstone pattern like the one printed on my real-world ceramic floor tiles.
Of course, the Minetest replica doesn’t have a bidet, air conditioning, internet access, hot water, natural light, or conveniently walkable 24-hour hamburger shops like my real-world apartment does. But it’s a lot tidier, and I can remodel it completely in another half-hour if I want. Moreover, I’m not likely to run out of space to put things, which in real life can be a problem; this world currently has about 1 km × 2 km generated horizontally, and I've dug almost 500 meters down, and it’s only 49 megabytes, very little of which is the underground palace I added the apartment replica onto.
Aboveground, the palace does have its own stand of lumber trees, a giant outdoor fountain I built and am using to irrigate a cotton crop, and a watch tower with a beautiful view of the sunrise; indoors, it has a mushroom cultivation area, a 49-square-meter dojo with a mosaic floor, chests full of copper and gold ingots, ovens baking bread from wheat cultivated upstairs, a fireplace, and a room illuminated through its glass floor by lava running below. (In another Minetest world, I built a continuously erupting volcano visible from my balcony that, unfortunately, burned down a forest.)
So, like nearly all video games, Minetest offers a sense of competence and progressively increasing power. Minetest is also a medium of expression like that provided by painting and CAD programs. But, probably most addictively, Minetest is a sort of animated dollhouse: a vehicle for a convincing fantasy of living a good life, though it is a life involving a great deal of smashing rocks and hauling them up mine shafts. Like literal dollhouses, you can play in it alone or with friends or even strangers; it supports sharing your virtual reality over a LAN or the internet.
Also, in some ways, it goes beyond literal dollhouses: it provides an illusion of travel. Like any first-person three-dimensional game, the screen contents are in almost constant apparent motion toward you, triggering your orienting response and making it easy to pay attention, and you can travel around, explore the world, learn where things are, and find more things.