People always love to talk about how DOOM can be ran on anything, from your average PC to a pregnancy tester (yes, really lmao) but Half-Life is also incredibly optimized and versatile, old android slider phones from 2013 can even run them! (yes, I did get Half-Life to run flawlessly on my LG Enact)

This is all possible thanks to an amazing Half-Life source port known as Xash3D. It's a source port made by Flying With Gauss that is VERY optimized and compatible with anything that runs android. From cars to even some smart fridges, if it has a screen with android and was made after 2012 it can probably run it. There also other devices that can run it too but we'll get to those later.

https://github.com/FWGS/xash3d/releases/tag/v0.19.2

That is the link to the APK and IPA files. For android, simply get the APK onto your device and install it, or use jailbroken iOS with something like AppSync (for unsigned IPA files) and install that. Xash3D is also available on PC with better performance then the Steam version. iOS 6 and Android 2.2 and above are supported, so a wide range of devices can run it.

Once you install the app, you can't just click "play" and have it work. It's not THAT easy, because that would be piracy and Valve would sue them. You need to provide the game files, but that's easy to do. I won't be going over the instructions here because Xash3D gives you them as soon as you open the app.

Anyway, once you're done, press run and you can play Half-Life! It's that easy! But Xash is supported on more than just Android and iOS. The 3DS, Switch, and I believe the Wii U at some point had working Half-Life builds. I won't be going over them since I'm not very familar with them, but a simple google search should lead you to the right direction. You can also get the game files from the original Half-Life CD as well.

There's also mod support! You should be able to find other versions of Xash3D that allow you to play the expansions and mods like echoes as well. Also, simple gamebanana mods work with it perfectly.