5 replies to this topic

[Fort Apocalypse]

Starting a thread for people's examples of doing crazy stuff in bB. This doesn't necessarily have to be anything useful. Just wild stuff that isn't documented (or at least not much) and is not necessarily "supported".

[Fort Apocalypse]

Flip the right-side of the playfield with CTRLPF $x0

Attached Files

•  ctrlpf00.bas   746bytes   16 downloads
•  ctrlpf00.bas.bin   4K   31 downloads

Edited by Fort Apocalypse, Mon Jan 21, 2008 9:45 PM.

[Fort Apocalypse]

Use ball as a whole playfield line with CTRLPF=$xF

Effects:
* ball changes entire line of playfield to height and color of ball
* ball is playfield color (COLUPF)
* left half of playfield is player0 color
* right half of playfield is player1 color

Attached Files

•  use_ball_line.bas.bin   4K   54 downloads
•  use_ball_line.bas   655bytes   20 downloads
•  use_ball_line.bas.asm.txt   28.18K   20 downloads

Edited by Fort Apocalypse, Tue Jan 22, 2008 8:42 PM.

[Nukey Shay]

http://nocash.emubase.de/2k6specs.htm

0Ah - CTRLPF - Control Playfield and Ball size
  Bit  Expl.
  0	Playfield Reflection	 (0=Normal, 1=Mirror right half)
  1	Playfield Color		  (0=Normal, 1=Score Mode, only if Bit2=0)
  2	Playfield/Ball Priority  (0=Normal, 1=Above Players/Missiles)
  3	Not used
  4-5  Ball size				(0..3 = 1,2,4,8 pixels width)
  6-7  Not used

 
In "score" mode, the playfield is drawn by COLUP0/COLUP1 for left/right half of screen (instead COLUPF in both halves). Intended to display 2-player mode scores at different colors by low-resolution playfield graphics (used by older games like Combat).

[Fort Apocalypse]

Wonder why CTRLPF=$xF makes the ball draw a line across the right side of the screen from it. That doesn't seem to be described in the documentation (or did I miss it)?

[SeaGtGruff]

Fort Apocalypse, on Tue Jan 22, 2008 11:17 PM, said:

Wonder why CTRLPF=$xF makes the ball draw a line across the right side of the screen from it. That doesn't seem to be described in the documentation (or did I miss it)?

The z26 and Stella emulators show different results-- z26 shows a blank screen. So, at least one of them, and possibly both of them, are wrong. You shouldn't count on this "undocumented feature" being available on a real Atari, because in my line of work, an "undocumented feature" is just a fancy name for a "bug"!

Michael