Monday, December 7, 2015

Door work and more

Ok, enemy spawning finally works right. There were a couple of minor bugs in my spawning code that I last posted (c'mon, nobody spotted them? I thought with a million eyes, all bugs are shallow? I guess that means I have a few less than a million readers that are also 6502 assembly programmers!) But I got the bugs taken care of.

I decided the next step, to try to get my brain interested in this project again, was to go ahead and start actually making the first dungeon. Awhile ago I posted a survey to see if I should re-implement the maps from the original Anguna, or make a new adventure. Everyone voted for a new adventure. But it sounds really fun to try to reproduce the first dungeon, at least. So that's what I started on.

And immediately realized that although I had worked out proof-of-concepts for my door code, it wasn't finished. Doors on the top worked. I hadn't finished doors on the bottom. Which required going back and modifying my display kernel code, which meant I was back to counting cycles.

But I think I have that working, finally.

I also originally only allowed for a left-side or right-side to be closed (if I wanted them both to be closed, I had to draw the room map with a permanently closed wall, which reduced that room layout's flexibility for use in other rooms).  But after playing with that, I didn't like it much. So I had to re-think how this was going to work.

Originally, I used the Atari "ball" graphics object, (which is a 1,2, or 4 pixel blob) extended vertically across the whole screen, to block off a left-side or right-side door. But if I wanted to block both at once, this wasn't going to work. (there's only 1 ball!) So instead, I counted and realized I had time to squeeze in one additional instruction in my code that pushes the background data to the right registers, so I could pre-load a byte in ram with a mask to be applied to the walls, and, OR that with the actual room wall data before pushing it to the display registers. Because I'm using a mirrored background, that could close both the left and right doors at once.

Both the left and right doors are closed! Hooray!


The next step is another part that I realized I never implemented: if you have a secret door that only opens when all the enemies are dead....well, it never opens.  Not because my code to open it doesn't work. But more because it turns out I never wrote that code.

So that's next!




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