Redditor BerryBerrySneaky has posted a guide showing how to access hidden menu’s of the Arcade1Up and access MAME, as well as add new games! All that’s needed is to solder a USB connector (such as the ones linked below) onto the motherboard, then plug in a keyboard and hit Escape!
Check out the threads for more details:
https://www.reddit.com/r/Arcade1Up/comments/a476im/hacking_the_arcade1up_34scale_mini_arcade/
Also, see this post for links to a $200 version of the Tempest / Asteroids cabinet: http://retrorgb.com/is-200-low-enough-for-arcade1ups-tempest.html