A Documenting of a Tetris CHIP-8 Game

This is my documenting of the Tetris game submitted to the fourth Octo Jam event.  Given this game's
large size, I will only show it fully documented and fragmented, with the explanations interspersed.
This game is notable, and I chose it, because it was apparently written by-hand, and I can see this.

The register usage is as follows, less detailed due to the game's large size:

V0 Serve as a scratch register, an index, and miscellaneous purposes.
V1 Serve as the horizontal sprite coordinate.
V2 Serve as the vertical sprite coordinate.
V3 Hold the piece rotation code, and later the height.
V4 Hold the piece code.
V5 Hold the next piece code.
V6 Hold the low score.
V7 Hold an initial key, and hold a shifting code.
V8 unused
V9 unused
VA Hold the high score.
VB Serve as a toggle.
VC Hold a counter.
VD Hold a counter.
VE Hold a counter, and indexed codes.
VF Hold key codes, manipulate the delay and sound registers, detect collision, hold constants, etc..

The game clears the screen, draws TETRIS, draws a symbol I don't understand, then waiting for a key: