'Guardian Aura' Bug Fix and miscellaneous other patches

[Norman Sword]

A flurry of posts whilst I sat with the above text in the editor.

[IRF]

Thanks Norman - silly mistake I made using LD A,(HL) instead of LD A,L (picking up an actual value from the item table, rather than picking up the index pointing at that value).

 

I notice the little optimisation at the end of the item-filter loop as well. :)

 

Hopefully with those edits applied, the 128 room version will work too.

Edited March 4, 2018 by IRF

[IRF]

; this code moves the tile in hl down by one line

 

;

xor a

ld d,a

ld b,8

loop

ld e,(hl) ;the current line

or d ;the line above

ld (hl),d

ld d,e

inc h

djnz loop

 

;

; a=the accumalative value of the bits drawn

 

;

 

or a ;if a value exists then the floor is still collapsing

 

This permits a one pixel line to be moved down the screen

How about this slight rewrite of the loop:

 

xor a

ld d,a

ld b,8

loop

ld e,(hl) ;the current line

or d ;the line above

ld (hl),d

ld d,e

ld a,h

add a,c

ld h,a

djnz loop

 

Set C=01 beforehand for regular crumbling tiles, or C=FF for bashing away at wall tiles from below(?)

Edited March 8, 2018 by IRF

[IRF]

Also, HL has to start off pointing at the top pixel-row of the cell in the case of a crumbly, or start off pointing at the bottom pixel-row for bashing a wall tile.

Coming from 'Move Willy', HL starts off pointing at an attribute coordinate (#5Cxx or #5Dxx). Use PUSH and POP HL to preserve that address, for updating the attribute of the cell to Air once crumbling is complete.

For a wall tile, use a similar approach as the 'old' crumbly tile code, in order to point HL at the bottom pixel-row:

LD A,H
ADD A, #1B
OR #07
LD H,A

For a crumbly tile, point HL at the top pixel-row by using:

LD A,H
ADD A, #1B
AND #78
LD H,A

The command in bold can be a common entry point to a shared part of the code (if the C register is used to increment or decrement H as per my previous post).

Edited March 14, 2018 by IRF

[IRF]

How about this slight rewrite of the loop:

 

xor a

ld d,a

ld b,8

loop

ld e,(hl) ;the current line

or d ;the line above

ld (hl),d

ld d,e

EX AF, AF'

ld a,h

add a,c

ld h,a

EX AF, AF'

djnz loop

 

Set C=01 beforehand for regular crumbling tiles, or C=FF for bashing away at wall tiles from below(?)

 

Update: you would need to preserve A (e.g. by bookending the new code with two EX AF, AF' commands), so that after the loop has ended, A still holds a cumulative tally of all the infilled pixels in the cell.