How One Game Runs Inside Another Game: The Four Techniques, Explained

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2026-10-01 · Explainer

Affiliate disclosure: This guide contains affiliate links. As an Amazon Associate, we earn from qualifying purchases at no extra cost to you. Learn more.

The most common reaction to these clips is that somebody must have faked it. The second most common is a vague guess about two games running at once.

The second guess turns out to be right for one of the four techniques, and completely wrong for the other three. They produce footage that looks similar and they have almost nothing in common underneath.

So here is what is actually going on, with a named example of each that you can go and check yourself. Once you can tell them apart, a lot of the "is this even possible" argument answers itself.

The Short Answer

Question	Answer
Can two games really run at once and share one screen?	Yes. One shipped project does exactly this and documents how.
Is that the usual method?	No. It is the newest and the rarest of the four.
Does this need source code for either game?	For three of the four, no. Mod support or a plugin loader is enough.
Which technique produces something you can download?	Any of them. The split is about finishing, not difficulty.
Do any of these run on a handheld?	One does. Sonic Robo Blast 2 is free and ready to run on 39 devices through PortMaster. The rest need the host game running first.

Technique 1: Two Games Running at Once

This is the one people guess at, and until last week nobody could point at a public example of it. Now there is one.

The example: SkyCraft. Minecraft inside Skyrim, released 30 September 2026, MIT licensed, source public. We cover the project itself in its own piece.

Two programs run on your PC simultaneously. Skyrim, with a plugin loaded into it. Minecraft, hidden completely, with no window and no sound. They share a block of memory that both can read and write, and they trade data every single frame.

Three problems have to be solved, and the way they get solved is the whole technique.

Whose physics wins? One game has to be in charge of the player or they fight. In SkyCraft, Minecraft wins. It runs your movement for real, then sends your position over, and the Skyrim plugin switches off Skyrim's own movement and moves the Skyrim player to that spot every frame. That leftover Skyrim player is doing real work even though you are not controlling it. It is what NPCs detect, what quest triggers check against, and what arrows fly at.

How does one game learn the shape of the other's world? Skyrim's collision gets read near the player and streamed across as a pile of plain boxes, at a fraction of a block in size. On the Minecraft side, a code injection appends those boxes to the answers Minecraft gets whenever it asks what is in the way. Then ordinary Minecraft physics runs against them. Nothing about gravity or jumping or step height was reimplemented, which is the point.

How do both end up in one picture? The hidden game renders only the things that belong to it. Blocks, dropped items, your first person arm, the hotbar and hearts. Those go into textures that are handed to the host on the GPU. The host composites them into its own frame, and crucially it compares depth, so a stone wall in the host world correctly covers a tower you built behind it. Both render in parallel each frame, the host waits a moment for the guest, and if the guest is late the host just shows the previous one again.

How to spot it: the two games' lighting and shadows match, because only one of them is actually lighting the scene. And the host game's own systems keep working in the background, which is very hard to fake convincingly over a long take.

Why it is rare: it is the most work by a wide margin, and it is fragile. It depends on the host game's exact version, on a plugin loader existing for that game, and on specific graphics features being available to pass textures between two processes.

Technique 2: A New Runtime That Hosts Both

Here nothing is injected into anything. Somebody writes a brand new engine from scratch, and that engine reads both games' data files.

The example: the 2010 Rust Rewrite Mashup. Modern Warfare 2, Skate 3 and a working Minecraft world in one program, covered here. It runs on IW4L, a from scratch rewrite of MW2 in Rust. You launch its executable and point it at your game folder. MW2 is never modified or even started.

This is the most work of all four in raw hours, and also the most robust once it exists. It cannot be broken by a patch to the original game, because the original game is not running. That is why this one shipped and kept shipping updates while flashier projects stayed as videos.

It is also the closest relative of a recompilation, though it is not one. A recomp converts the original game's own code into a native program. This rebuilds the game's behaviour in new code. We cover that distinction in the decomp and recomp explainer.

How to spot it: the clip shows a launcher or an executable that is not the original game's. The requirements will mention bringing your own copy of each game for its data files.

Technique 3: The Guest Drawn as Raw Pixels

The oldest trick on the list, and by far the easiest. The guest game runs as a small program whose output is a rectangle of pixels, and the host simply draws that rectangle on something in its world. A screen, a wall, a monitor in the corner.

The famous example: VM Computers. A Minecraft mod that has you order PC parts from an in game tablet, assemble them into a case, and end up with a real virtual machine, running through VirtualBox, inside your Minecraft world. Boot Windows 98 on it, open MS Paint, then load DOS Doom and play it on a monitor that exists in Minecraft. It was downloaded over 327,000 times and got picked up everywhere when it landed.

The catch is that it has not been updated since April 2021, so it needs Minecraft 1.16.5 and specifically VirtualBox 6.1. There is a small fan port for newer Minecraft with a few hundred downloads, which is a different and much less proven project. Do not mix the two up.

The minimal example: HytaleDoom. Doom rendered as raw pixel data inside Hytale and controlled from the game. The creator's own README calls it horrible code written in two or three nights for a video. As of 1 October 2026 it is source only with no published release, which makes it a perfect demonstration of something being completely real and completely unplayable at the same time.

This is also the family that every "Doom runs on a pregnancy test" story belongs to. The host does not understand the guest at all. It is showing you a picture and forwarding your button presses. VM Computers is the purest version of the idea, because the thing drawing the picture is a whole emulated computer.

How to spot it: the guest game sits inside a frame or on a surface rather than in the world. It does not interact with host geometry, lighting or physics, because there is nothing to interact with. It is a video feed you can press buttons at.

Why it matters anyway: it is the only one of the four that is genuinely approachable. A competent modder can do it in a weekend, which is exactly what happened here.

Technique 4: Rebuilt in the Host's Own Engine

No second program, no shared memory, no pixel buffer. Somebody sits down and reimplements one game's systems using the host game's own tools.

The examples: Halocraft, which taught Halo 3's physics engine how to handle destructible Minecraft style voxels years after Halo 3 shipped. the voxel engine built inside Super Mario 64, which generates infinite terrain with biomes and lighting on a console with 8MB of RAM. And the biggest one in progress right now, Morrowind in Elden Ring, which its creator describes as the most complex mod ever created. Roughly half of it is done, including Morrowind's entire map and interiors, and it reads files straight out of your own Morrowind installation rather than shipping any.

This is the oldest and most common technique, and it produces the most convincing footage, because everything genuinely is one game. There is no seam to spot. The cost is that nothing comes for free. Minecraft's block breaking did not arrive with Minecraft's code, somebody wrote block breaking in Halo's scripting from nothing.

The Largest Version: Rebuilding in Another Engine

Push this technique far enough and the host game stops being a host at all. You take a game's engine, rebuild a different game inside it, and ship the result as a standalone thing people launch on its own.

That is Black Mesa, which rebuilt Half-Life in Valve's Source engine and ended up a commercial Steam release with official Steam Deck support. It is the only project in this entire category that has ever properly finished. It is also Skyblivion and Skywind, rebuilding Oblivion and Morrowind inside Skyrim's engine, at 13 and 14 years of development respectively and both still unreleased.

And it is Sonic Robo Blast 2, a Sonic fangame built on a modified version of the Doom Legacy engine by Sonic Team Junior. That one has been going since the late 1990s, it is free and GPL licensed, and it matters more than the rest for our purposes. See the handheld section below.

How to spot it: it looks perfectly integrated, because it is, and the feature list is usually narrower than it first appears. A full reimplementation of another game's systems is enormous, so these projects pick the handful of mechanics that sell the idea.

The handheld relevance: this is the only technique with a route onto cheap hardware, and the Super Mario 64 one is why. Anything that fits in an N64 cartridge runs on any handheld with an N64 emulator. It has been unreleased since May 2025, but if it ever ships it is the one entry here that matters on a forty dollar device.

So Was the Elden Ring One Real?

This is the question the whole wave hangs on, and the honest answer has two halves that people keep collapsing into one.

When that clip went viral, the most popular theory in the replies was that two games must be running at once, with positions and entities passed between them. At the time that was a guess with no public example behind it.

As of SkyCraft, it is a documented technique with a working, downloadable build and a design document explaining every handoff. So the concept is no longer speculative. Something that sounded impossible two weeks ago is now a thing a person demonstrably did.

That does not verify the Elden Ring project. As of 1 October 2026 it still has no public repository, no release and no download, which means nobody outside its creator can check what it is. Our verification checklist is the five minute version of how to run that test on any clip.

Those two statements sit together comfortably. The technique is real and that specific build is unverified. Deciding one proves the other is the mistake that made this whole wave confusing in the first place.

What This Means for Handhelds

There is exactly one of these you can install on a cheap handheld today, and it comes from technique 4.

Sonic Robo Blast 2 is free, ready to run, and available on 39 devices through PortMaster. Sonic Team Junior built it on a modified Doom Legacy engine, it is GPL licensed, and the PortMaster package ships every file it needs, so you supply nothing. PortMaster lists no hardware requirements against it, which means it reaches the cheapest devices in the catalogue. SRB2 Kart is a separate package on the same 39 devices. Both are about 184MB, which is the only real caveat. Our PortMaster guide covers installing them.

It is a fangame, and Sonic Team Junior say so themselves: their README states they are not affiliated with SEGA or Sonic Team and claim no ownership of SEGA's intellectual property. The engine work is theirs and it is open source.

For everything else, the host game has to run on your device first. Elden Ring does not run on an Anbernic. Skyrim and Minecraft both do in some form, but SkyCraft needs a Windows plugin loader and a GPU texture handoff that is Windows specific, so a Steam Deck is where the conversation starts and ends. Halo 3 through the Master Chief Collection does run on a Deck, so Halocraft is a realistic Deck proposition, installed like any other PC mod. Our Decky and Nexus guide covers doing that without dropping into Desktop Mode. Black Mesa is the easiest Deck entry of the lot, since it is simply a game you buy on Steam that has official Deck support and gyro controls.

The other exception is technique 4 on old hardware, where the constraint does the work for you. 8MB of RAM and an N64 cartridge is a target every handheld can hit, which is what would make the Super Mario 64 voxel engine matter if it ever shipped.

And if what you want is just Minecraft on a device you carry, none of this is the route. How to play Minecraft on a retro handheld covers four working options, two of which install in about a minute.

Check Handheld Prices on Amazon

Telling Them Apart in Thirty Seconds

What you see	Likely technique
Guest game on a screen or surface, ignoring the world around it	3, drawn as pixels
A standalone launcher, no host game involved, one game in another game's art and engine	4, at its largest scale, like Black Mesa or Skyblivion
Perfect integration, narrow feature set, host's own art style	4, rebuilt in the engine
Launcher or executable that is not the original game's	2, new runtime
Guest's full UI over the host's world, host's own lighting on guest objects, host's NPCs and quests still alive	1, two games at once

The running list of which projects have actually shipped is in games rebuilt inside other games, and we keep it updated as builds appear.

Frequently Asked Questions

Yes. SkyCraft, released on 30 September 2026, runs Skyrim and a hidden copy of Minecraft as two separate programs that pass data through shared memory and share rendered textures on the GPU. Its public design document describes every handoff. It is the newest of the four techniques and the only public example of it we know of.

How do people put one game inside another game?

There are four distinct methods. Running both games at once and passing data between them. Writing a new engine from scratch that reads both games' data files. Running the guest game as a pixel buffer that the host simply draws on a surface. Or reimplementing the guest game's systems using the host game's own modding tools. They look similar in a clip and are completely different underneath.

Which method is the easiest?

Drawing the guest game as raw pixels inside the host. The host does not understand the guest at all, it displays a picture and forwards your inputs, which is the same family as every story about Doom running on an unlikely device. HytaleDoom was written in two or three nights by its creator's own account.

Does putting a game inside another game need the source code?

Usually not. Three of the four techniques work from mod support, a plugin loader or the game's data files. Rebuilding a game's systems inside a host engine needs no source for either game, and running both games at once needs a plugin loader for the host rather than its source. Writing a new runtime from scratch is the one that involves heavy reverse engineering.

Why do so few of these ever get a download?

Most are demos of skill. Proving it can be done and posting the clip is the goal, and turning that into something strangers can install is a much longer job with no reward attached. Deep mods also break every time the host game patches, and rebuilding one live commercial game inside another draws attention from two publishers rather than one.

Can any of these run on a retro handheld?

One can. Sonic Robo Blast 2, which is Sonic rebuilt on a modified Doom Legacy engine, is free and available ready to run on 39 devices through PortMaster with every file included, so it works on very cheap hardware. SRB2 Kart is the same. For the rest, the host game has to run on your handheld first, which rules out nearly all of them. A project built inside an old console game would be the other exception, because the original hardware's limits become your guarantee, which is why a voxel engine inside Super Mario 64 would run anywhere if it ever released.

Can you really play Doom inside Minecraft?

Yes. The VM Computers mod builds a genuine virtual machine inside Minecraft through VirtualBox, so you assemble a PC from in game parts, boot an old version of Windows on it and run DOS Doom on a monitor that exists in your world. It was downloaded over 327,000 times. The catch is that it has not been updated since April 2021, so it needs Minecraft 1.16.5 and VirtualBox 6.1.

What is the difference between a game inside another game and a game rebuilt in another engine?

A project like SkyCraft runs inside a live host game, so Skyrim is genuinely running while you play. Black Mesa, Skyblivion, Skywind and Sonic Robo Blast 2 take the fourth technique to its limit instead: they rebuild one game inside another game's engine and ship a standalone thing you launch on its own, with no host game underneath. Same family, much larger scale, and the only ones in this category that have ever properly finished.

Was the Minecraft in Elden Ring video real?

Nobody outside its creator can say, and as of 1 October 2026 there is still no public repository, no release and no download for it. What changed is that the popular theory about how it would work, two games running at once with data passed between them, is now a documented technique with a shipped example in SkyCraft. That makes the concept plausible. It does not verify that particular project.

Written 1 October 2026. Technique 1 is described from the README and design document of SkyCraft, technique 2 from 2010-rust-rewrite-mashup and iw4L, and technique 3 from the VM Computers CurseForge page and HytaleDoom, all retrieved 1 October 2026. Technique 4 draws on our existing coverage of Halocraft and the Super Mario 64 voxel engine, on the creator's public progress reports for Morrowind in Elden Ring, on the SRB2 repository and PortMaster's ports.json for Sonic Robo Blast 2, and on published reporting for Skyblivion, Skywind and Black Mesa. We have not run any project named on this page, and publish no performance figures for any of them.