Thank you for your motivation and some pointers
Since my first post I didn't get much work done, but editing the basic level tilemap is now working (with some quirks).
I just want to finish some minor things, before I will push this very preliminary version to GitHub.
Besides the level tilemap and the obvious things like size, music, tileset, time there are three additional parts to the level description. After the level tilemap is a list of RAM positions for sprites like DK, Pauline and the Mario starting position. The RAM position basically translates directly to offset in the level tilemap. This is very straight forward but not yet editable because I am still indecisive how to display these sprites, and because ripping the graphics straight from the ROM like I do for the level tiles will not work or would need much more work than it is worth...
The other two parts are before the level tilemap and are "optional" and both not fully understood by me. The first is somehow some more sprites and RAM address. The very first level uses this for example, but it just contains DKs sprite again, and testing the level without it seems to result in no visible difference... I have not really looked much further into this.
The last part is related to switches. I already had a quick attempt to follow its contents in the debugger, but lost track. More or less blind editing of the bytes mostly results in no response from flipping the switch or in messing up the whole level upon loading...
March 03, 2014, 02:35:56 pm - (Auto Merged - Double Posts are not allowed before 7 days.)
the first post now contains a link to the GitHub repository.
As stated in the previous post, editing of the tilemap works, if you use more tiles/sprites than fit inside the gameboy's VRAM the level is not displayed correctly. The sprites can be displayed as black boxes and moved around.