Conquering the World, Pixel-by-Pixel
Territorial.io is just about the simplest and most straightforward realtime global warfare simulator there is. You pick a spot on the map and your job is to grow out from your pixel to the point where you rule the world. Or enough of it to meet the victory conditions. There are up to 512 others trying to do the same too, so a bit of skill and a lot of luck is needed to fulfil your manifest destiny. By clicking on the map you expand your land holdings. The more pixels under your control, the more rapid your population grows and therefore your army. The latter is controlled by the percentage bar. Expand with low numbers and the more people stay at home to reproduce, but less land is taken in. The higher the numbers committed, the slower the growth in the short term and the greater one's vulnerability is to attack. The same applies when attacking enemies, which will quickly surround you. If you commit large numbers to take out an opponent, you'll have no juice left in the tank to fend off attacks from others. This isn't a problem in single player mode below harder difficulty level. The bots are limited and are easily squished. On very hard though, the bots will attack whoever is the weakest. And as their numbers aren't nerfed like they are at lower difficulty levels, they're going to win. Repeatedly. The trick is to go after the weakest bot on your borders (usually) and make sure you don't expend too many troops, because as soon as your population count goes below a neighbour - particularly in the late game - you're toast.
Single player is good for practice, but multiplayer is where the fun is at. Again, up to 512 human players can descend on one of 14 maps with the numbers made up by bots, and battle commences. The AIs here are uniformly weak and purposely designed to provide population fodder for the humans. Alliances of convenience can then spring up to take down big players, or persistent annoyances or, on several occasions I've seen, players who take on racist or Neo-Nazi monickers (what is it with wanting to cosplay the Third Reich in war games?). There are also team modes in addition to the standard battle royale that allow players to gift troops to one another to help out in fights over far flung corners of the globe, which adds a new layer of strategy. And there are now semi-permanent teams that have emerged on Reddit, and a clutch of YouTube channels going heavy on Territorial.io content. Not bad for a free game that's only existed for a blink of an eye. It is a fiendish game where blunders are shown no mercy, and one cannot believe how stupid other players can be.
Ultimately, games of this sort disproportionately attract Hitler enthusiasts, empire nostalgics, and hardcore nationalists is because the logic of play plugs straight into a key aspect of their imaginary. Just as children up until the 1960s were taught to be proud of the territories shaded pink on the class world map, this helped inculcate a decontextualised, abstract notion of greatness. This elided power with the amount of land a country claimed, so infant patriots might have fancied Britain as the best and most powerful nation because its imperial land area outstripped everyone else. Extrapolated into adult minds, empire maps fixed one's place in the world. Britain is best and therefore I am better than other peoples.
Territoriality plays a similar role in all nationalisms. On the white nationalist far right and its identification with Nazism, the empire Hitler briefly ruled - found on ten-a-penny war maps of Nazi Germany at its fullest extent - speaks not only to the military prowess of the regime, but also the (imagined) historic viability of their rotten politics. If it could happen once and nearly succeed, it might happen again. It doesn't matter that their atrocious view of the good society was utterly crushed by the combined militaries of politically inferior governments and racially inferior communists, the deterritorialised territory lives on in their brains as an inspiration. Squiggles on maps out of time, out of context, and completely divorced from the brutalities that made thoes lines briefly possible.
Territorial.io is an excellent, diverting casual game. Just remember to crush racists and neo-Nazis when you spot them in-game.