Thursday, 10 January 2013

Bet you got square eyes :)

9th January 2013

Back in 2010 I wrote my first ever tape loader game for the C64 (Cool). That game was called "Moo-Tilation". It was a funny shoot 'em up game, in which you had to defend your hapless cows from being abducted by aliens. In the late 2011 I wrote yet another C64 loader game, called "Happy Blocks", inspired by one of the games I played on FB. HB was a game in which you shift your block, having to avoid getting smashed by the falling blocks. The game required a lot of action.

So then. If you remember those two games quite well. There's a new kid in town. Back in 2007 I wrote a game for a demo group, Civitas called "Square Pit 64" now it's back once again, resurrected as a tape loader game with a slightly new look and a different Euro-disco style tune. I originally planned to rip the original Square Pit 64 game source and implement it into the loader. Unfortunately, I had some problems doing exactly that, so I decided to quickly program the game from scratch, with the aid of the existing resources. I originally was going to go for a techno/trance style theme for the game. Where every time the drum kick came on screen, the screen flashed. I decided not to bother at the end, as the result turned out quite bad.

Instead, I added some pulsating flash routines on to all of the sprites, apart from the small square (Which will stay as white). I also added a fitting track into the source, and tested the game inside an IRQ interrupt. Seemed to have worked quite nicely, but there appeared to have been something wrong. I noticed the scores were placed in the wrong place after a new game was started. I soon fixed that problem. Finally the game was working. So now it was time to remove the IRQ interrupts, and link the game to the Thunderload tape loader.

The biggest mistake I noticed in 2012 was that Thunderload Series Six loader never was compressed, because I had to keep on changing the scroll text and tunes for it. Well, this time round, I decided to compress Square Pit, using Exomizer's level compression mode. Then assemble a decruncher source from the Exomizer, itself. I had to use DASM for this. After assembly and compression and linking the decruncher to the compressed source, I linked the final build to the tape loader source. I altered the LoaderGame init address to call the decruncher routine (Which I placed at $5000) and the set the play address at where the main loops in the game occurred. I altered the batch file to build the .tap using SQUAREPIT.PRG instead. I picked a program to be loaded after the loader game, as a test guinea pig, which was of course "Trance Sector". I tested the tape loader system and it worked a treat :)

Here's a video of the tape loader in action.

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