Retro-Ball for the Apple II Featuring "Video-Sync"
7Retro-Ball is an obscure Apple II game written by Alick Dziabczenko and released by the little known Sierra Software in 1980. Sierra Software had no relation to Sierra Online, which was still known as On-line Systems at that time. It was later ported to the C64. No Apple II emulator that I know of can run this game, and the reason why is its requirement of "Video-Sync". Video-Sync is a hardware method to detect the Apple II's vertical blanking signal. Back in 1980 the Apple II and II+ did not have any port or interrupt to tell the CPU when display was in vblank and not drawing graphics. This was added to the IIe, //c and //gs in various ways.
However back in 1980 those computers did not exist and a software method for the II+ was not published until 1982. In order to provide a vblank status signal, Sierra Software bundled a cable with the game. This cable connected the lone video output pin on the Apple II+'s mainboard to the cassette input jack. As the game came on disk the cassette input would not otherwise have been used. The software would poll the cassette input port to determine when the video hardware was in vblank and then time the drawing of the updates to the graphics to avoid flicker and slow, jerky movement.
I am running this game on my Apple IIe. As I do not have the original packaging, I had to build my own Video-Sync cable. This was really easy to do with only a bit of solder, a 3.5mm solderable mini-jack and a wire with a female connector that could be placed on the auxillary video output pin of the Apple IIe. The sound was recorded via a microphone placed close to the system, so you can hear "all sounds" which went into the making of this video. :D The capture device is a GV-USB2
This is an image from an original disk, only recently made available. If the Video-Sync device is not detected, the game will throw an error message after the title screen telling you to install the device and will boot no further. This game also came on an pirate compilation disk with a simple text-based title screen. This pirate version will get to the main gameplay screen but will freeze waiting for a Video-Sync signal. Because the Video-Sync was not used in any other Apple II game, no emulator that I am aware of supports it. The game has never been modified to use any of the video blank detection capabilities of the Apple IIe, //c or //gs.
The game is a take on table air hockey and it is controlled via paddle controllers. The knob controls the direction in which the paddle is to go and the button "hits" the paddle (or fires a rocket according to the game's manual). You can score a point by hitting the white line on the edge of your opponent's side of the table, and the longer the ball touches that line the more your score increments. You can also score a point if the ball spends four seconds on the other side of the table without going over the center line. The game ends when one player gets 10 points or the time runs out.
I do not have a pair of Apple paddles so I have had to make do with a self-centering joystick axis. I imagine the game might be a little easier to play with true paddles. When it comes to the two player mode I am playing both players. This game was impressive as a tech demo, but once you figure out the controls it is very difficult to score points because you have to hit the white line dead on center to score a point. Also you can only direct the puck in the four cardinal directions, more granular control of the ball's direction is not available.