The other real challenge is that you have to build your entire game using just 128 bytes of memory. Not kilobytes, bytes. You don't have the luxury of having

The other real challenge is that you have to build your entire game using just 128 bytes of memory. Not kilobytes, bytes. You don't have the luxury of having a single scanline of the screen at memory at once. There is no caching of anything. You have just enough memory for a handful of current state variables and that's it. Luckily your program is running out of ROM so you don't have to load it before you execute, but even with that it's an incredibly tight fit.