[stella] Death Derby Milestone

Subject: [stella] Death Derby Milestone
From: Glenn Saunders <mos6507@xxxxxxxxxxx>
Date: Mon, 24 Feb 2003 05:02:36 -0800

Okay, I've been holding off on posting to the list until I felt I made more significant progress with the game. Since I haven't seen a post here in a while, now might be a good time.

I've been corresponding back and forth with Thomas privately in order to fix some of the remaining kernel glitches and they are all gone except for one (which is probably a minor fix, read on).

I'm not ready to have end-users play with it yet on Atari Age, but I'm far enough along that I'd like to solicit opinions from the list.

I've been adding in one feature a day to the code on average, so things are moving along steadily.

For instance, take a look at how I did the score routine. I rolled this one from scratch based on memories of reading disassemblies (for the doubled characters and the masking). Anyway, I'm using indirect indexed Y loads there and I know there is a faster way to do it. If there is a way I could speed it up and drop the interlace and do all the work on one scanline, it's worth pursuing. Note that I'm trying to use as little vertical real-estate for the score as possible to make room for the cars.

If anyone has an example of a game that uses 3 2-digit score chunks using players I'd take a look at that too. It's just that I'm trying not to have to reposition the players during the active kernel, and I'm also trying to be purposefully minimalistic to emulate the 1st generation game aesthetic (in which case the score might remind you of something like Canyon Bomber).

But if the general feeling is that it would be better to do it with sprites, to more closely match the coin-op score fonts, then I'll make an effort to do that.

This current binary supports the Y-cable interface (maybe for now on let's call it the GearBox adapter). Wiring information for this can be obtained here:


Right now the game only responds by toggling the blocks in the corners of the screen to indicate forward or reverse gear. Tap forward to kick the car into forward gear, tap back to go into reverse. A visual cue is important since I don't want to force people to hold the joystick forward or back to stay in forward or reverse gear. The joystick is just a latched toggle switch. So I need something in the score to indicate that. If I had used the difficulty switches, I wouldn't need the indicators as much, at least if you were using a six-switcher ;)

The rotation of the cars is completely independent of the joystick functions and they don't interfere with eachother.

I've also implemented the Color/BW switch for an authentic grey-scale display.

The current movement of the gremlins is probably pretty close to what it will be in the finished game (although right now there is no AI so they are just moving in a single fixed direction). It gives you a taste of the stagger-step diagonal way they move, but I'm not at all happy with the way the code handles the movement. It's pretty kludgy, but it works enough for this demo. I'm hoping nobody notices so much that the vertical movement on the gremlins is in 2-scanline jumps and that the gremlins never start on the same scanline. Unless I slow the gremlins down any more than this, I don't think the 2-scanline jumps are a problem. I also tweaked the running animation and I'm hoping everyone agrees that these missiles really do look like honest to goodness players. Because the animation of the legs is so fast it almost looks like I'm painting both legs all the time but there are frames where I'm just animating a single leg going through a sweeping motion. There are only two extreme poses that feature two legs, one with a leg outstretched forward and one with a leg outstretched backward.

Pressing fire on the driving controller will move either car up. I'm just putting in the hooks for the controllers. I still have to work on a system of animation that accounts for rotation and acceleration.

If anyone has some thoughts on how best to do that, please post them. I'd love to hear it, and wouldn't want to have to reinvent the wheel.

The current glitch I have is when the green car crosses the top of the screen it looks like its graphic isn't getting zeroed out properly.

If anyone (in addition to Thomas) could review the code, I'd appreciate it.

In the meantime, I'll be updating my journal pages. I've been too busy coding day in day out to maintain the journal of late.



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