This is a repository for archiving interesting things about the JJ1 alpha--also known as G_MAIN, Universal Game Editor, and Vertigo--since trying to record things in chat services will only result in them being buried and forgotten.

To begin with, to run the game you'll need DOSBox or similar, but you can copy any existing DOSBox shortcut you have (for example, for regular JJ1) and just point it to G_MAIN.EXE.

There are four LEVEL#.### files included with the game. LEVEL0.000, the default, is by far the biggest, but you can play LEVEL0.001 and LEVEL1.000 by running the game with the command line arguments G_MAIN 0 1 and G_MAIN 1 0.

LEVEL9.999 is pretty much just LEVEL0.000 again. According to fc.exe, it differs in only two bytes, 0x226 and 0x228.

G_HELP.TXT is the most useful of the various text files, because it includes instructions for using the level editor, G_EDIT.EXE.

The F10 key enables an ingame debug mode that shows numbers onscreen describing the player's position, the current number of events, and similar. If you try to exit the game (by pressing Esc) while in debug mode, the camera scrolls vertically for a while, including graphically rendering some unrelated memory.

Lots of images are included, but not everyone has programs that understand BBM and LBM images, so I've converted them to PNG for convenience. I haven't tried reading the BLOCKS/SPRITES files so I don't know if these are the exact versions of the graphics used in those compiled files or if there were changes made at some point.




A few tiles should be familiar from Megairbase.

Level maps, cropped to just the used areas:










The layout data starts at 0x13 in level files and is an uncompressed array of 512 * 32 * 2 bytes, but it's sorted by column rather than row, so the first two bytes are the leftmost tile in the top row, then the next two bytes are the leftmost tile in the second row, and so on. Each two bytes use the same format as JJ1: the first byte is the tileID from 0-239, the bottom seven bits of the second byte are the event, and the top bit of the second byte shows the black background.