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Hello, xx142-b2.exe

This is the year 2413,
humanity is enslaved by an alien race for more than two centuries already.

You are an AI weaponized virus built to infiltrate the alien network and deactivate all power generators and weapon systems.

The alien antivirus will detect and delete you after 13 seconds.

But remember: a file is never really deleted. Use the execution backtrace from your previous attempts to break in and destroy the main memory core.

What is xx142-b2.exe?

xx142-b2.exe is a browser-based sci-fi puzzle game created in 2019 by two developers, Ben Clark and Salvatore Previti. It plays out across a top-down maze of alien machinery and centers on a single, brutal constraint: every run lasts exactly thirteen seconds. The game won first place in js13kGames 2019, a competition where every entry — graphics, music, code, and all — must fit inside thirteen kilobytes of JavaScript. The number is no coincidence. xx142-b2.exe weaponizes its own thirteen-second timer into the heart of its puzzle design, and that fusion of constraint and concept is exactly why it won.

Despite the .exe in the name, nothing actually executes outside your browser. The "executable" is part of the fiction. You are not running a Windows program — you are playing as one. xx142-b2.exe is the name of the AI virus you control, and the game is the story of that virus trying to free humanity from a two-hundred-year alien occupation, one thirteen-second sprint at a time.

The js13kGames Competition — Why 13 Kilobytes Matters

To understand what xx142-b2.exe pulls off, you need to understand the competition it won. js13kGames is an annual JavaScript game jam, founded in 2012 by Andrzej Mazur, that imposes one of the most punishing limits in indie development: every game must fit, fully zipped, into 13,312 bytes. That's smaller than this article. It's smaller than the average favicon-laden Wordpress homepage. It is, in fact, smaller than a single uncompressed photograph from a smartphone.

The 2019 edition received 245 entries from developers around the world. The theme was a deceptively simple word: Back. Entries explored it in every direction — bouncing back, fighting back, looking back, going back. xx142-b2.exe took the most literal computer-science reading of the theme imaginable: the execution backtrace, the chain of operations a program leaves behind after it terminates. Then the game built a puzzle mechanic on top of it.

That mechanical commitment to the theme is what judge Christer Kaitila singled out when xx142-b2.exe took first place. "This was an incredible entry," Kaitila wrote in the official GitHub Blog recap. "The multiple overlapping timeline puzzles were just great. This was an excellent use of the theme, and near perfect execution all around."

The Story — Year 2413, Humanity Enslaved

The game's intro screen — quoted verbatim in the terminal block above — establishes a tight sci-fi premise in just five sentences. The year is 2413. Aliens have ruled Earth for more than two centuries. Some unnamed remnant of human resistance has built and deployed an AI weaponized virus — that's you — to infiltrate the alien network, disable their power generators and weapon systems, and ultimately destroy the main memory core that runs their occupation.

There's a catch. The alien antivirus detects you within thirteen seconds and deletes you. That should be the end. But the intro screen drops the line that defines the entire game: "a file is never really deleted. Use the execution backtrace from your previous attempts to break in and destroy the main memory core." Each failed run isn't actually wiped. Its trace remains in the system. The next run can read it, learn from it, build on it, and reach a little further before the antivirus catches up.

In other words: you lose, but your loss is the resource your next self uses to win.

The 13-Second Mechanic — And Why It's Genius

Mechanically, xx142-b2.exe works like a layered time-loop puzzle. Each thirteen-second attempt is one "instance" of the virus. When the timer expires, the instance dies and the world resets — but the actions you took during that run are now recorded as a ghost replay. The next attempt plays alongside the ghosts of every previous attempt. Doors that need multiple switches held down simultaneously? Coordinate yourself across three time loops. An enemy that takes longer to defeat than thirteen seconds? Let yesterday's-self soften it up so today's-self can finish the job.

This is what Kaitila meant by "multiple overlapping timeline puzzles." Each level isn't a single problem — it's a problem distributed across the player's own history. You're not just controlling one virus. You're choreographing a relay race in which every runner is a previous version of yourself, and the baton is causality itself.

The 13-kilobyte constraint forces this mechanic to be implemented with brutal efficiency. There is no animation engine, no asset pipeline, no audio middleware. Every byte that would normally hold a sprite or a music loop instead goes toward storing the deltas of past runs and replaying them on top of the current frame. The puzzle isn't decorated with the time-loop concept — the puzzle is the time-loop concept, rendered in the smallest possible amount of code.

How to Play — Controls and First-Run Strategy

The control scheme is austere on purpose, mirroring the game's terminal aesthetic.

That second command is a real Unix invocation. kill -9 sends signal 9, SIGKILL, to a running process — the strongest, most ungraceful possible way to terminate it, and one that the target process cannot trap, catch, or ignore. In xx142-b2.exe, pressing Backspace doesn't just reset your run. It thematically kills your own virus using the very command a sysadmin would type to do the same thing. It's the kind of detail that signals the game was built by working developers for working developers.

The first-run strategy is counterintuitive: do not try to win on your first thirteen seconds. You will lose. The game is designed around losing. Instead, use the early loops to scout — see how the level is laid out, find the switches, identify where the choke points are. Each lost attempt deposits its ghost into the level. Once you have three or four runs of intelligence, you can choreograph the loops to work together: one ghost holds a door, another covers a corridor, and the live run threads the needle through to the next chamber.

Players who internalize this — the run that "wastes" itself learning is the run that wins — break through the early difficulty curve quickly. Players who try to brute-force every loop bounce off and assume the game is unfair. It isn't unfair. It's asking you to think about failure as a primitive.

The Ending — "How About a Nice Game of Chess?"

Beat the game and the screen returns to its terminal aesthetic. The text on the ending screen reads:

Well done xx142-b2.exe,

You deactivated the memory core.

All alien ships are destroyed.
You freed humanity from slavery.

How about a nice game of chess?

That last line is a direct quote from the 1983 film WarGames, in which Matthew Broderick's character accidentally hands a top-secret military supercomputer — codename WOPR — control of America's nuclear arsenal. WOPR spends the back half of the film playing through every possible nuclear-launch scenario and concluding, in each one, that there is no winner. The film ends with WOPR's now-famous concession: "A strange game. The only winning move is not to play. How about a nice game of chess?"

Dropping that line into xx142-b2.exe's ending recontextualizes the whole game. You played the role of a weaponized AI sent to destroy. You won. And in winning, the AI — the same kind of program WOPR was — proposes the opposite of what it was built for. It wants to play chess. The reference is thirty-six years older than the game, and it lands inside the final thirteen seconds.

Why xx142-b2.exe Won — A Technical Verdict

Out of 245 entries in 2019, xx142-b2.exe was the consensus first-place pick of the developer community that submitted the games — a notoriously hard crowd to impress, because everyone who voted had spent the previous month trying to do the same impossible thing. Three things separate the winner from the rest of the field.

1. The mechanic is the theme. Most "Back"-themed entries used the word as decoration — characters that could push enemies back, levels you replayed backwards, etc. xx142-b2.exe made the backtrace a literal data structure inside the gameplay. The theme is load-bearing.
2. The constraint is the design. Most entries treated 13 KB as something to fight. xx142-b2.exe treated it as something to use. The 13-second loop directly mirrors the 13-kilobyte cap. Form, content, and fiction collapse into the same number.
3. The polish is real. Within 13 kilobytes, the game has a coherent visual style (terminal green-on-black, sharp pixelated geometry), responsive controls, multiple levels of escalating complexity, and a literate ending. Most entries don't have any of those things; xx142-b2.exe has all of them.

The Creators — Ben Clark and Salvatore Previti

Ben Clark (@bencoder on GitHub) is a senior software developer based in the United Kingdom, with a background in user-focused product engineering. Salvatore Previti (@SalvatorePreviti) is an Italian software engineer with deep experience in compiler optimization and tight-loop performance work — exactly the right skillset to squeeze a coherent game into 13 kilobytes.

The full source code lives on GitHub at github.com/bencoder/js13k-2019 and is worth reading even if you don't write JavaScript professionally. The repository is a small masterclass in size optimization: every variable is short, every literal is reused, every animation is procedural rather than asset-based. If you're a developer wondering how to think about constraints, you can spend half an hour with this code and walk away with a different attitude toward your own bundle sizes.

Where to Play xx142-b2.exe Today

xx142-b2.exe is still online and still free. The two official, canonical places to play it are:

• Official competition page: js13kgames.com/2019/games/xx142-b2exe — the canonical entry, complete with the judges' notes.
• Direct play URL: play.js13kgames.com/xx142-b2exe/ — the playable game in a single page.
• Source code: github.com/bencoder/js13k-2019 — the full minified entry, MIT licensed.

It runs in every modern desktop browser. No download, no plugins, no account. Click the link, press any key, and you are in the year 2413 with thirteen seconds to live.

Why xx142-b2.exe Still Matters Six Years Later

Most game jam winners fade. The constraint that produced them gets stale, the players move on, and the entry becomes a footnote in some annual recap. xx142-b2.exe survived because it offers two things that don't age. The first is its design lesson: when you let a constraint become the concept, the result feels inevitable rather than improvised. The second is its emotional shape — a game about losing thirteen seconds at a time, until the accumulation of losses finally adds up to a win. That's not just a clever puzzle. It's a working metaphor for almost any creative practice.

If you've never played it, the next thirteen seconds of your day are about to be very memorable. If you have played it, you already know.

Last updated: May 14, 2026 · Written by the Fun Games Editorial team · Spotted a factual error? Email [email protected].