Turning a Raspberry Pi into a retro game station is easily one of the most popular Raspberry Pi projects around. If you want to make that project portable, you'll need a screen but the most common one, the Adafruit PiTFT, requires a little effort to get it working for more advanced games.
When you connect the Adafruit TFT (or any other display for that matter) to the GPIO, it bypasses the Pi's video hardware. This means that any games that depend heavily on the GPU or OpenGL get screwed up. The good news is that Adafruit's worked out a solution. First things first, you'll start by getting RetroPie up and running. From there, you'll need to install a bunch of different software, tweak a few settings, and dig into a variety of configuration files. Once you're all done, your display will finally work properly, with some performance gains. We've covered afew differentportable Raspberry Pi retro game stations before, and with Adafruit's guide you should get the performance boost you need to play some more advanced games.