Old World, a historical 4X that feels like a step forward for the genre, borrows its most radical mechanic from Microsoft Word. Hit Ctrl-Z, and you can undo any action.
Typically this is a function reserved for typos, but developer Mohawk Games gives us the power to turn back time across warfronts, city districts, and rural pastures. Did you send out a battalion of spearmen to the wrong sector and muck up your adjacency bonus? Undo. Did you misread the defense integers and accidentally sacrifice a settler in a profoundly stupid way? Undo. Did you decide your heir was going to study philosophy when, on second thought, maybe he'd be better as a mathematician? Undo. Literally every action in Old World can be immediately rolled back with no consequences. The game will not call you a nincompoop for your tactical blunders, nor will it dock your score of any points at the end of the era for the amassed Ctrl-Zs. In Old World, everybody makes mistakes.
I cannot tell you how revolutionary this feels. I'm a longtime Civilization player, and there have been so many incidents where I absent-mindedly dispatched a worker to an empty farm, only to be struck by the horrifying thought: No, no! I wanted him to build a mine instead! What am I doing! It's too late. That farmer is stuck plowing a field, reducing the overall efficiency of your game plan by a maddingly imperceptible degree.
We've all been there: disciples stuck between borders and barbarians with nowhere to go, naval offensives gone awry as it becomes clear that Augustus's walls are neutering your lowly triremes, Great Merchants idling in a Holy District because you mistook it for a Commercial District. The Sid Meier doctrine is punitive. Players are punished for their lack of attention; to be a good leader, one must always be focused on the details. But Old World makes that attitude look outdated. It's true that history can't be changed, but in the wondrous fantasy of 4X, shouldn't we be able to correct a couple of unsightly oversights in the margins?
Firaxis is most likely hard at work on Civilization 7, and I pray that we see the "undo" feature there so we may never misplace a trader ever again. Ideally, this new dawn will metastasize across countless other strategy games, too. Can I please reset my gunner's position in XCOM? I really thought that wall provided more cover than it did. (This would open up the problem of undoing after a sniper misses a 95% shot—one of the classic, agonizing frustrations in all turn-based games—though maybe it's high time that injustice was washed away in another fashion anyway.) Paradox should also be taking notes. Maybe I accidentally slotted some failson dunce into my spymaster slot and would prefer to swap them out with a much more competent vassal without provoking an insurrection in the kingdom?
Old World isn't the first strategy game to feature an undo button, though it's a rare recent example. The Panzer Corps series have them, and Panzer Corps 2 lets you customize how it works in the settings so you can alter whether you're allowed a takeback after discovering an enemy or not. Another example is Invisible, Inc. which is built around having a limited number of resets.
Maybe in some contexts this is sacrilege, and players should be forced to live with all of their mistakes forever. But seriously, what's more fun to play? A sickly empire, reeking of neglections and potholes, stumbling towards a pyrrhic triumph? Or a well-oiled juggernaut that has leaned upon countless undos on its path to glory? We both know the answer, deep down.
There are some obvious genre limits to this suggestion. Nobody can "undo" a headshot in Call of Duty or a dropped combo in Mortal Kombat. As hilarious as it is to imagine, nobody should be allowed to "undo" a really, really bad left turn in SnowRunner, because that is not in the spirit of those games. But turn-based strategy has increasingly started to present all of its tactical information on the surface. There are no dice rolls in, say, Into The Breach, or Endless Legend, or Old World. You know exactly what's going to happen from the second you press the button. Within that arena, the Ctrl-Z glory ought to stick around for good. Microsoft Word had it all figured out from the start.