This version is almost exactly the same as the final
release. The only major differences are that the both
the difficulty switches are reversed from the final and that a
little bug was fixed in the joystick read routine.
Interestingly the difficulty switches follow what is printed in
the manual, so the manual was probably based on this
version. It is unknown why this was reversed for the final.
Prototype Differences
A bug in the joystick read
routine was fixed
The left difficulty switch for music on/off is
reversed (A=Off / B=On)
The right difficulty switch for speed is reversed
(A=2 Speeds / B=3 Speeds)