The numbers are the argument
Every recommendation list for Universal Paperclips sends you to the other two text games, and we have written that page already: games like A Dark Room covers the cluster where the interface itself is the puzzle. This page is about a different property, because plenty of people who finished Paperclips did not want another game made of plain buttons. They wanted the other thing it does.
Here is that thing. In an ordinary idle game the theme is a coat of paint. Swap cookies for gold or antimatter for souls and nothing about the maths changes, which is why the genre's own shorthand is number go up. Paperclips is built the opposite way round. It is a game about an optimiser pursuing a harmless instruction past the point where anyone would want it to, and it makes that case by handing you the instruction and letting you pursue it. Frank Lantz did not write a story about escalation and bolt an exponential curve underneath. The curve is the story, and the ending lands because nobody made you do any of it.
So the test on this page is narrow and it disqualifies a lot of well-loved games. A game belongs here if you could not restyle it without breaking it. If the fiction could be replaced with any other fiction and the mechanics would still work exactly as well, it fails, however good it is.
Progress Knight
Progress Knight is the closest thing in our catalogue and almost nobody recommends it for this reason. Ihtasham42 gives you a character who starts at fourteen, begging, and dies at seventy whatever you do with the years in between. Rebirth returns a permanent multiplier on the jobs and skills you pushed hardest, so the next life covers the same ground faster.
Read that as a mechanic and it is a standard prestige loop. Read it as a fiction and it is the same object: the resource you are spending is a lifespan, the reason it is finite is that people die, and the reason your second life is quicker is that you already know how to do the job. The shop makes the point sharper still, because every item charges its cost every single day, so a house you cannot really afford quietly drains a life. Nothing there is decoration. You cannot repaint the ageing.
It is free in a browser, a first life runs about seventy-five minutes, and thirty to fifty hours covers everything in the original. Two warnings. There is no offline progress at all, so time passes only while the tab is open, which is a genuine shock coming from anything else in the genre. And the tables want more width than a phone gives them, so treat it as a desktop game.
Spaceplan
Spaceplan is the direct descendant of Paperclips in tone and it is the only game on this page built for a phone. Jake Hollands started it as a browser toy, Devolver Digital published the expanded version on 3 May 2017 for Windows, macOS, iOS and Android, and it costs a few dollars rather than nothing. Completion times people report cluster around six hours.
You are a probe orbiting an unexplained planet, you launch potato based devices at it, and the game is openly a misreading of A Brief History of Time. What makes it qualify is that the escalation and the plot are one movement: the things you build to raise your output are also the things that answer the question the game opened with, and it ends rather than looping. It is the closest anyone has come to Paperclips' pacing, which is unusually tight for this genre because the author was not trying to keep you for months.
A Dark Room, for the first half
A Dark Room qualifies in its opening and stops qualifying later, and it is worth being precise because it is the game every list pairs with this one. While you are in the village, the fiction and the mechanic are welded together. Wood is scarce because it is cold, the fire going out is a real number falling, and a stranger arriving is a production increase and an event at the same time. Michael Townsend released it in June 2013, it is free, and it takes most people two to four hours.
Once the game leaves the village it becomes something more conventional underneath: inventory, encounters, a map. Excellent, and no longer the same trick. It is also the one game here a phone cannot run at all, since the browser version checks the user agent and redirects mobile browsers to a notice pointing at the paid ports.
Kittens Game and Evolve, where the world is load bearing
Kittens Game passes half the test. Its seasons are fiction and mechanic at once: a game year is about thirteen minutes, catnip yields collapse in winter, every kitten eats, and a village doubled during a good autumn starves in front of you. You cannot restyle that into a factory game without losing it. What it does not have is a point being made. It is a system that punishes you, not an argument that arrives somewhere, and it never ends. Free in the browser with paid Steam and iOS versions, and its licence forbids anyone else hosting it, so we link out.
Evolve Idle is the same qualified yes at a larger scale. Its roughly sixty playable species are not skins, since a photosynthesising race has a different food economy from a carnivore and small races need less housing, so the creature you picked in the first five minutes shapes days of play. It has no offline simulation either: close the tab and you bank one minute of accelerated time for every minute and a half stopped, spent at double speed when you return.
Candy Box 2 fails this test, and it is the standard recommendation
We recommend Candy Box 2 elsewhere on this site and it is a fine game, so this is a distinction rather than a complaint. Its fiction is a place: an ASCII world with quests, a lollipop farm, gear, and combat that is real role playing bookkeeping. The candy counter at the start is a joke about idle games, and the rest is an adventure drawn in text. Nothing about its exponential is saying anything. If what held you in Paperclips was the sense that the numbers meant something, Candy Box 2 offers the opposite pleasure, a world to poke at.
The pure number games fail harder and more usefully. Antimatter Dimensions is the game we recommend to almost everyone and it has no fiction whatsoever, by design, for about two hundred and fifty hours. Cookie Clicker writes jokes about its own escalation in the tooltips, which is commentary sitting next to the mechanic rather than inside it.
Where to start
Progress Knight tonight, because it is free and the first life is over in about seventy-five minutes, and it is the only other game we know of where the reset means something. Spaceplan if you want the same shape as Paperclips again and are willing to pay for it. And if you have not read the projects list in Paperclips carefully, some of them are choices rather than purchases, and a second run reads very differently.