A substrate does not have to be solid to compute. It is possible to make a computer purely from a liquid. I demonstrate this using a variety of experimental prototypes where a liquid carries signals, actuates mechanical computing devices and hosts chemical reactions. We show hydraulic mathematical machines that compute functions based on mass transfer analogies. I discuss several prototypes of computing devices that employ fluid flows and jets. They are fluid mappers, where the fluid flow explores a geometrically constrained space to find an optimal way around, e.g. the shortest path in a maze, and fluid logic devices where fluid jet streams interact at the junctions of inlets and results of the computation are represented by fluid jets at selected outlets. Fluid mappers and fluidic logic devices compute continuously valued functions albeit discretized. There is also an opportunity to do discrete operation directly by representing information by droplets and liquid marbles (droplets coated by hydrophobic powder). There, computation is implemented at the sites, in time and space, where droplets collide one with another. The liquid computers mentioned above use liquid as signal carrier or actuator: the exact nature of the liquid is not that important. What is inside the liquid becomes crucial when reaction–diffusion liquid-phase computing devices come into play: there, the liquid hosts families of chemical species that interact with each other in a massive-parallel fashion.

I started to learn chess from four years old… I spent 26 years playing, analyzing, trying to improve my chess ability with many different ways, with different changing methods; with many new ways of training. I think I did everything. Sometimes I thought I was addicted to chess, because sometimes without tournaments, I was not so happy. Sometimes I struggled to find other hobbies to make me happy. This match is the deepest reflection of my soul. I could not control my mood. I will cry. I will burst into tears. It was quite a tough tournament for me. I feel quite relieved.

FYI, beyond being "inkless", both of these are marketed as "forever pens" or "everlasting pens" (and to me, that's the interesting aspect of these) — but the $6 one isn't actually a real "forever pen"; it's just a (silver-core) pencil.

From the $6 pen's Amazon description: "Working principle: the nib rubs on the paper to decompose the alloy metal molecules and leave them on the paper surface". In other words: this is a pencil. It will wear down over time, and need new nibs. (You could also tell by the fact that they sell replacement nibs for this "pen." A "forever pen" shouldn't need replacement nibs!)

IMHO the only reason someone would be interested in the $200 pen is the "forever pen" aspect. (As, if not for that, if you want an "inkless pen", why not just buy a regular, cheap pencil?) The $200 pen does achieve the "forever pen" claim, insofar as it chemically reacts to paper without the tip wearing away. In contrast, the $6 "forever pen" isn't actually a "forever pen" (or "everlasting pencil") as it claims to be. It's an impostor product, a GameStation 360 kind of thing. So it's somewhat of an invalid comparison to review these as two products in the same category.

Also, re: erasability, think about it this way: if the markings can be erased, then those markings are not caused by a chemical reaction with the paper, but rather as a deposit on top of the paper. A real "forever pen" is necessarily a non-erasable pen, because it's necessarily a pen that's doing something chemically to the paper, rather than leaving part of itself on top of the paper. (Which is also why they call it a "pen" rather than a "pencil" — pens are writing instruments that do something permanent to the paper, while pencils leave something on top of the paper that can be rubbed away.)

The secret to ordering the best thing on the menu is to look for sleeper hits, which are dishes that may seem unassuming or out of place on the menu but are unexpectedly delicious. The author suggests taking a chance on these dishes, even if they are not the restaurant's most famous or popular items, as they can often be a chef's passion project or an underappreciated gem. The article provides an example of a citrus-glazed turnip dish that became a sleeper hit at a restaurant in New Orleans.

Jimmy Cauty went to KEVICC school in Totnes in the early ’70s but got into trouble for day dreaming and drawing wizards instead of working on his maths equations, but when his Lord of the Rings poster became an international smash hit selling over 6 million copies worldwide he was forgiven.

Jimmy moved to London in 1977 to start a band and never drew another wizard poster. He got into trouble for driving his tank to a road protest but later when his rave band The KLF became an international smash hit he was forgiven again.

These days Jimmy doesn’t make records, draw wizards, drive tanks or burn money but instead makes dystopian model villages.