Changes

= Machines =

Machines often varied by their design and, unlike consoles, were often tailored to just one game. Games were designed to eat as many quarters as possible, which is emulated with the "Coin" key. Some games have a service mode (mapped to F2 in MAME) with menus meant for the arcade owner to set dipswitches for difficulty, censorship, language, and most importantly a "Free Play" mode that allows players to continue as many as they want without requesting more coins. Sometimes, similar menus meant for developers (labeled debug or test usually, sometimes requiring a developer BIOS like with some Neo Geo games) are left in the game too.

==Discrete circuitry-based==