The short answer for how this desktop calculator can run so many different games — from original NES to more modern titles like “Doom 3” — is its somewhat unnecessarily powerful internal components. The GHLBD comes with a 1.8 GHz 32 bit Quad-core ARM Cortex-A7 processor and 1 GB of RAM, along with a full color touch screen display and a USB-C connection port intended for charging. Android 9 is also pre-installed, which leaves the door open for software modification. There isn’t much internal storage, but the GHLBD can work with an external USB drive and there’s more than enough out of the box to run some classic NES games.
Of course, it’s not going to simply play video games as soon as you turn it on. It will require a bit of setup by first swiping down on the screen and opening the Android settings, then turning on USB Debugging. Once that’s done you can start installing apps (i.e. emulators) and games (i.e. ROMs) through the USB connection. In practice it should work much like loading similar software onto an Android phone, though the hardware is likely simpler than what you’re used to.
Once everything is loaded up you can start playing games on your calculator — albeit with some inexplicable frame rate issues that can be seen in Taki Udon’s video (even with NES titles).