Minecraft

Minecraft is made of cubes of the same size. Any cube can be removed and placed somewhere else, and there are almost no other rules. The terrain is generated procedurally from a numeric seed: what's stored is the way to compute the map, so the world has no set boundaries and keeps being built as the player walks onward.

There are two modes. In survival, resources have to be mined, hostile creatures appear at night, and a building is needed first of all as shelter. In creative mode there are no restrictions, and only building remains. Redstone blocks add a separate layer: they carry a signal and work as logic elements, from which doors, counters and whole computing circuits are assembled. The public alpha appeared in 2009, version 1.0 in 2011, and all that time the unfinished game was being sold. Early sales, together with an open format for mods and private servers, shaped the fate of the project more than the graphics, which is what talk about it usually comes down to.