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Atari XL/XE Space Harrier Conversion Project

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7th October 2004

Although progress seems slow, Stage 2 is now nearly complete with new graphics and the reworked routines mentioned in the August 2004's diary entry. The music for the end boss needs to be done though - at the moment it's just using Stage 1's Squilla the dragon's music. I'm not worrying too much about the music for now, as I hope to replace the current work in progress music with some higher quality work, maybe using a tracker such as the excellent Raster Music Tracker

The routine used to gradually speedup the end bosses fireballs, (such as the dragon in the demo version) wasn't very effective - In fact I wonder if anyone noticed that that was supposed to be happening in the demo. The Bresenham line draw method used to move the various alien missiles in the game doesn't lend itself very well to achieving that effect. However this month I've made it work much better. (In case you're wondering what the Bresenham line draw method is, it's a way of drawing lines that avoids having to do a division calculation to work out the slope of each line. Most 8-bit processors like the 6502 really don't like doing division much - they're pretty slow at it. Anyway - a big thank you to Mr. Bresenham for figuring out how to do it first. It's one of those wonderful little insights, that when you finally get it, you kick yourself and say, "Of course! Why didn't I think of that?"). Anyway, in the movie clip below, hopefully you'll notice that the bosses' fireballs do speedup better as time goes by.

Since I won't be releasing any more code until all the level and graphics data is in the game for a Beta version, I've put together a movie clip of what Stage 2 will be like on the Atari. See Insert Coin.

To elaborate a little on the changes mentioned in the last diary entry:

• The overlaid parallax scrolling backgrounds of the original are now included. This was quite a hard trick to pull off without any hardware support from the machine, especially in a bit-mapped screen mode as opposed to a character based one
• Sound sample playback has been improved. The demo version could only move the man slowly when a sample was playing, and the rest of the screen had to stay static. Now everything can carry on moving (albeit with a few limitations)
• Graphics routines no longer rely on undocumented 6502 instructions for greater speed

I think it was worth starting over on the game to incorporate some of these changes - I hope you'll agree if you live long enough to see the finished game!

Here are a few screenshots showing some of the reworked graphics from Stage 1 and 2

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