Can You Avoid Death in the ZX81 Game Stick Shift?


It will take a good eye and strategy to survive on the dangerous road.

Stick Shift game play, ZX81 screen shot, Steven Reid 1985Dodging games were the rage back in the early í80s. Wanting to add my own take on the genre, I created Stick Shift, Novemberís program of the month. The goal is simple. Dodge other cars, oil spills and spikes while not crashing into the wall. Mess up? Well, itís game over for you. Donít fret though, it isn't that hardóyet.

Shift and dodge.
The game play is pretty simple. Using the arrow keys, you move (5 & 8) and shift (6 & 7), make your way through each stage for extra points. If you do, the course gets narrower, making the dodging harder.

You start the game in low gear. Shift up to speed things up. Itís not much, but enough to notice. As things get tight, you can shift down to the slower speed. Note that you wonít get any points when moving slower. So, use it when it helps, but speed up again when you can.

Also note that you can drive over the edge of the track before the side wall. There is a catch though as you wonít get any points, or worse. If you are in low gear, youíll lose a point. This game play is unusual for my programs, but makes sense in a driving game.

Those obstacles seem well spaced.
Code wise, Stick Shift works as a pair of loops. The outer loop acts as the the stage counter. The inner loop acts as the obstacle counter and will shrink as the game progresses. This makes the course more littered as you progress. It also shortens each stage.

As noted, you can shift speed up or down. Line 300 does this by setting a variable with some time consuming math. As Iíve noted before, you can slow down the ZX81 using its SIN, COS and other complex math functions. To make the code shorter, I also used the ZX81ís unique PI constant.

The rest of the code is interesting as well, but I wonít go into details. Iíve talked about the various techniques in the past. There are a few places I could change, but wonít. The program is great as is.

Thatís a wrap.
And there you have Novemberís program of the month. A great little game that is fun with a good amount of difficulty.



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