Monday, 1 November 2010


A fan of Luigi alerted me of this game. A Defender clone for DOS, released in 1990. It may look simplistic, but simplicity is one hell of a lot easier to blog about than the stuff I've been trying to push out for the last week... and it's got a few tricks up its sleeve which makes it that extra bit special.

Jumpjet is a game that was developed by a man known as "Monte Variakojis". It was mostly written in assembly language, bar the menu system which was built up with C, and sold as a shareware title... presumably with purchasable other bits. As you can see though, for a game released in 1990 it's not the most graphically appealing of titles, and predictably, this game failed to sell in large quantities. Now, like so many other DOS games, sales are slowed down by not only its primitive looks, but because the average joe can't understand DOSBox, even though it's incredibly easy. But come on dude, it's written in assembly language - that takes effort.

Jumpjet can technically look a bit better than this. There are, in fact, four graphics options, several of which are a bit hacky. There's a 320x200 4-colour CGA mode which one can rely on, and there's support for Hercules graphics cards if you're a fan of high-res black and white. But there's also two 16-colour EGA modes - "high resolution" and "low resolution". Traditionally you'd expect the high resolution mode gave the best results, and it does... sort of.

But the problem is Jumpjet's definitions of "high" and "low" resolutions aren't quite what you may expect. All the resolutions here are designed with CRT monitors in mind - the old pre-Windows ones which would take any image and scale it up to the right width and height (most of the time). I don't want to get too technical (because then I might get things wrong) but the "low", 640x400 setting contains blockier graphics than the "high", 640x350 alternative. 640x350 is, however, quite ugly when windowed, so for all of the screenshots on this page, I've gone for the low resolution 640x400 mode... which is technically 50 rows of pixels more than high resolution. Try explaining that to your digital TV fans.

It's all to do with how pixels are rendered on the screen buffer and whatnot, but regardless of which setting you choose, the game was clearly designed for computers that are well past their sell-by date. Surprisingly though, despite not having the best graphics options in the world, the game supports adlib or soundblaster sound cards (though don't go expecting music). Good to know you're not going to be punished on all fronts then.

Though a Defender clone at heart, Jumpjet puts you in... well... a jump jet and makes you complete four different missions, ranging from blasting bombers to blowing up oil tankers. The game is fairly short as a result, but it's a challenge, and of course it's padded out with a couple of time-based bonus missions.

There is but one big flaw with this game, assuming you can look past the sub-par graphics - other jets. Rather than attempt any sort of strategy, the enemies mindlessly fly into you at any given moment. As with Defender you've only got one life, but unlike Defender enemies are only interested in destroying your ship. Of course, being hit is great fun, as your plane spins out of control and blows up into tiny red pieces, but it would be just as fun for the enemies to go down in such a spectacular fashion.

The game relies a bit more on gravity than Defender does. The missiles which you fire, for example, curve downwards making them suitable for hitting ground targets. This gives the game a reason to introduce ground-based enemies and targets, such as tanks. But the game isn't overly realistic in its approach either. You can actually manouvre your plane at full speed while on the ground with its wheels out. Crazy stuff.

Overall it's not a flawless package, but the game is fairly easy to find and the shareware version is free to download. Of course, arguably the official DOS verison of Defender is just as easy to find, but it's nice to have a game that's different once in a while.

1 comment:

  1. Jumpjet was written as an experiment and with the idea to support a 1.77MHz 8088 microprocessor. It was a good high school project in 1985. It was decided to release it as shareware in 1990.

    Nonetheless, the game runs 18 frames per second (standard DOS timer speed of 55ms). Everything written from ground up supporting the graphics devices and the AdLib sound card. The "text" menu was written in C from the ground up as well.

    You can still find the author at

    Cool post. Keep it up.