Mr. NOP (NOP Software) presents LadyBug - For the Commodore PET

Navigate your ladybug throughout the maze while collecting food. Swing the doors to block the predators from
reaching you. Some levels have faster enemy speeds, level 4 has an invisible maze.


Technical notes:
---------------

After reviewing feedback on my first game (Oil's Well) I decided to implement an option to re-define the keys for
laptop users, etc. 

Different PET models read the keyboard matrix values differently which necessitated different versions of this game.
The IRQ vectors used in the high score screen are also different between the PET models.

The maze isn't the most challenging and the source code can be modified to change the maze layout. No changes to the
machine code are required if you decide to modify the screen layout.

The key lines in the source code to make the game compatible on other PET machines are as follows:

Lines 1022 and 2900 - Pause on and off
Line 4700 and on - Read keyboard for player control
Line 3660, 3724 and 3922 - Initialize and reset the IRQ

The default keys are 2,4,6,8 on the numeric keypad. You may need to redefine them to work on the 2001/30xx PETs.
Some PETs use location 151 to read the keyboard, the 2001 uses location 515.


PET 2001 Bugs
-------------

In attempting to convert this game to the PET 2001 I ran into an unusual problem. The game uses the standard $FFD2
Kernal routine to clear the screen. In the 2001 version the clear screen symbol showed up as the actual symbol rather
than clearing the screen. To fix this I wrote a routine at line 5600 to manually clear the screen. This brought
about another issue in having the new maze displayed beginning at the top left of the screen. I attempted to print
the cursor home symbol using the $FFD2 Kernal routine but it too appeared as a symbol rather than sending the cursor
to the home position. For this reason the high score screen and new maze screens remain bugged.
You're welcome to try to tackle this issue. It could simply be that the computer is in quote-mode.

In all versions of the game there exists the possibility that the random ? icon may appear inside the enemy box, making
it un-obtainable.

The game has been play tested under WinVice on PET 30xx and 40xx models without any issues.

Released April 4, 2013 in Ontario, Canada

nopsoftware (at) hotmail.com