I should contact Disch and see if he’ll let me host a copy of his document here.

I’m trying to write blog entries as I program the game so the ideas are still fresh in my mind when I write. I’m still playing catchup though. My game engine already has sprite movement with background collision working. I’m itching to make a new video and put it up, but I’m going to wait until the blog posts catch up to that point. Also I haven’t talked about sound at all, but I have a basic music engine working in the game. I’ll get there eventually though.

In the meantime, I recommend this document by Disch:

http://nesdevhandbook.googlepages.com/index.html

Looks like you commented in the thread over at nesdev, so you’ve probably read it already, but it’s worth reading several times. I pretty much follow his program structure verbatim, except that I don’t buffer the room drawing (I turn the PPU off).

Here’s my main loop so far:

forever:
jsr do_frame ;see Disch’s doc
jsr handle_joypad
jsr update_hero_sprite
jmp forever

handle_joypad checks for arrow presses. If there are any, it sets a hero_moving flag and sets her direction. update_hero_sprite does the actual movement, checking for collisions and changing rooms if the hero reaches a room boundary. It also cycles the sprite animations.

Thanks for the kind words!

I know this is jumping the gun a bit, but it’d be great if you could devote a future post to the overall structure of your game design. I know that’s a general subject, but it’d be great to see something catered to the peculiarities of the NES. For instance, how do you switch from title screen to the game, then to an end state? Where do those things go in code? What is the main loop and what happens there? Those are the kind of concepts I find confusing.

This is fascinating to read so far. No one’s done a step-by-step design doc like this for NES before, especially for an actual multi-screen game. Nice work.