The debate over whether or not Half-Life 3 will ever happen has been burning for years now. If you've ever played a video game, you've probably heard all about it: Valve built one of the best first-person shooters ever with Half-Life 2, released a pair of excellent downloadable episodes, then put the series on ice for more than a decade.

Of course, with the company's recent foray into virtual reality, rumors of Half-Life 3 are more rampant than ever.

It's the reason why so many Valve fans are willing to spend hours searching through lines and lines of code looking for any tiny scrap of information. Sadly, these searches are in vain the vast majority of the time — this time, however, the fans may have actually found something.

In anticipation of the HTC Vive VR headset's preorders going live, Valve released a virtual reality performance test — basically, a short demo that determines whether or not your rig can handle VR. The test itself isn't all that interesting — but the assets tucked away inside definitely are.

You may be wondering to yourself, "What's up with this picture of D0g? Wasn't he in Half-Life 2?" Well, that's the thing — that's not D0g's Half-Life 2 model. It's something new.

While it's still definitely unfinished, the folks over at ValveTime discovered that this particular version of D0g is far more complex than his original incarnation — namely, his body is far more complex, sporting a number of new cosmetic details. It's an older model, true, and one that's made its way online before — but if Valve isn't working on Half-Life 3, as some supposed employees have reported, why is there an updated version of D0g present in the tech demo's files?

On top of that, not only is D0g just the first of several Half-Life 3 assets found in the demo, Half-Life 3 isn't the only Valve game with assets in the performance test. A number of Left 4 Dead 3 textures were also found buried within the tech demo, including those for a character known only as "Retired Engineer":

Plus, there's a Left 4 Dead-themed room filled with items from the previous games:

At first glance, the above video seems like a jumbled mish-mash of broken code. There are Error models everywhere, there's nothing to do and there's seemingly no point to it. So, why would Valve go out of its way to put Left 4 Dead 2 assets inside it? Why include the textures for a character that supposedly doesn't exist yet?

Unsurprisingly, it only gets stranger from there: a number of different Portal demos were also included in the performance program, along with a somewhat-generic spaceship cockpit and other assorted rooms. The big question is ... why is there so much extra stuff buried inside a two-minute tech demo?

Now, before fans start losing their minds, it's important to remember that this does not mean any of the unannounced games present in the performance test are now confirmed. There's no way of knowing just how old any of these assets are, and they could simply be leftovers from projects cancelled long ago. As always, until Valve makes an official announcement (which it probably won't), absolutely nothing has been 100 percent confirmed.

That being said, there's an awful lot of stuff floating around in that tech demo — perhaps Valve hasn't been relaxing quite as much as fans thought it was ...

For each and every asset found in the tech demo, head on over to ValveTime.net.