Games is in heavy development and some known problems haven't been properly fixed yet, though if you want to push Games further, you will find in this page known workarounds to some of its problems or ways to extend it.
Please understand though that we do not recommend to do what is explained in this page and we take no responsibility to what could happen.
Games relies on libretro cores to run ROM games. Proper libretro cores are needed to make those games work depending on their original platform.
The current version (3.18) of Games supports NES, SNES, Game Boy (Color) and PC-Engine games with the correct Retro plugins installed; some other systems are known to work with varying results, and as such are not officially supported yet (those are Game Boy Advance, Sega Master System, Game Gear, Mega Drive/Genesis and Sega Saturn).
Nintendo 64 is known to not work, as the libretro cores usually require to render OpenGL, which Games doesn't support yet.
To correctly display the game icons for Steam games (when the game provides one), be sure to check "Create a system application icon" in the Steam installation dialog. Please note that not all Steam games provide a usable icon.