In other words it works on RAW METAL and doesn't require an Operating System."
The second statement doesn't quite follow the first. You can certainly write a 16 bit x86 assembly DOS application.
It's still awesome, though, and the code is really cleanly written and easy to follow.
Because the code is so nice, this would be a fun project to try to port to Protected Mode with its own HAL and maybe drivers for one set of hardware (perhaps QEMU's). Could be a fun experiment in why OSes are hard and x86 is painful.
In other words, it's using BIOS for input, but not drawing.
Also looks like boot.asm uses the BIOS to read the rest of the program...
Then you could easily chainload to Floppy Bird on a HDD from other bootloaders (like WinNT5 & NT6), with no changes to the main ASM program.
EDIT: the comments in boot.asm refer to sectors 1 & 2 since they are the first 2 sectors of the floppy, these two are officially numbered 0 & 1 in a disk editor or DD command.