Polygon's Charlie Hall recently posted a video tour of one of the most mind-blowing Minecraft builds I've ever seen. As Hall floats through and around an ingeniously made 1 KB hard drive that exists entirely within Minecraft, its creator Cory Littley walks both him and the viewer through its meticulous construction.
Littley's hard drive (like the Minecraft calculators and such that have come before it) relies on redstone, an item in the game that conducts a current used to power various devices. In my experience, redstone's simplest applications are easy enough to wrap your head around. If all you need are a few lamps, powered rail cars, or maybe an automatic door it's not hard to get a handle on how to use it, but things get exponentially more complicated the larger and more intricate your project is. That's what makes Littley's hard drive so incredibly impressive, even if it's barely big enough to hold the text of this post.
Don't just take my word for it: Watch the tour for yourself on Polygon.