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Luigi Ruffolo
10-23-2020 at 01:05 AM
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A first-person shooter on a humble TRS-80 CoCo

Nick Marentes is an Australian programmer. In his project archive, he told the story behind the development and the marketing of each of his games (he started in the early eighties). It's very interesting reading.

This is an extract from his article on Gate Crasher.

«For a long time, it was being debated if the Color Computer could create a true 3D game along the lines of the PC classics, Doom or Wolf 3D. Many said that the Color Computer, as many of the early 8-bit machines, was too slow to do the necessary 3D calculations required to render each scene at a decent enough frame rate to make a fast paced action packed game.

But one man was able to provide a glimmer of hope on this subject, John Kowalski. He had developed an algorithm that did the necessary calculations fast enough and created a demo program to prove it. The demo was called Gloom and in it, one could navigate around a 3D environment using a stock standard Tandy Color Computer 3 and it ran at a good frame rate.

This impressed everyone but there were many who felt that the final proof would be to create a full game. I decided to take up the challenge and Gate Crasher was the result. A "Wolf3D" style game featuring a full 360 degree 3D environment, explosive 2 channel digital interrupt driven sound and five levels of the hottest action seen in a CoCo game for years! This game clearly proved that 3D gaming of this type is possible even on an old 2 Mhz 8 bit computer.


The biggest challenge for me in this game was making everything run at a descent frame rate. This was accomplished with the aid of John Kowalski's "Gloom" 3D environment algorithm as well as heavy use of self modifying code. Gate Crasher represents a milestone in Tandy Color Computer gaming in that it is the first true full 360 degree, free movement solid 3D action game of this type for this machine. The game uses an unofficial 128 x 96 x 16 color graphics mode. Even utilizing double buffering, each screen only takes up 6K of memory, reducing the workload on the CPU to update each display frame. A further optimized version of the dual channel interrupt driven sound routine used in my last game allowed explosive sound effects to be had without too much CPU overhead.

Yes this game had it all...the player's gun would bob up and down as he walked, you could hear your footsteps, your gun recoiled when it fired, security doors that can only be opened by cracking the color coded locks, your gun would make a cool reload sound when ammo was found and the evil CEO had a classic evil laugh!


I was aiming at this game being released for the upcoming PennFest 2000 (see next project page). I knew the Color Computer market was getting smaller and smaller as time went on and I felt that most sales of this game would be had at that fest.

I was right. About 40 copies of the game has been sold to date, making it less than my last game, Pac-man. Even though Gate Crasher represents a milestone for 3D action type games for an old 8-bit computer, the market has shrunk so much that I felt that my game programming days for this computer have come to a close. This was to be my last game for the Tandy Color Computer».

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