1.1 --- a/build.py	Fri Mar 21 22:14:42 2014 +0100
     1.2 +++ b/build.py	Fri Mar 21 22:51:54 2014 +0100
     1.3 @@ -515,6 +515,12 @@
     1.4               monster_right_offset,
     1.5               monster_right_max_offset)
     1.6      
     1.7 +    scenery_rows = 16
     1.8 +    extra_rows = 7
     1.9 +    top_char_row, top_monster_row, top_row = 0, 0, 0
    1.10 +    bottom_char_row = scenery_rows + extra_rows - 3
    1.11 +    bottom_monster_row = bottom_row = scenery_rows + extra_rows - 1
    1.12 +    
    1.13      char_rows = range(6, 13)
    1.14      rows = range(13, 29)
    1.15      banks_char_rows_low = map(lambda x: (0x3000 + (x * 0x140)) & 0xff, char_rows)
    1.16 @@ -538,6 +544,20 @@
    1.17               ",".join(map(lambda x: "$%02x" % x, bank2_char_rows_high)),
    1.18               ",".join(map(lambda x: "$%02x" % x, bank2_rows_high)))
    1.19      
    1.20 +    screen_oph += (
    1.21 +        "; Define the vertical extent of the player area in terms of rows.\n"
    1.22 +        ".alias scenery_rows %i\n"
    1.23 +        ".alias extra_rows %i\n"
    1.24 +        ".alias top_char_row %i\n"
    1.25 +        ".alias top_monster_row %i\n"
    1.26 +        ".alias top_row %i\n"
    1.27 +        ".alias bottom_char_row %i\n"
    1.28 +        ".alias bottom_monster_row %i\n"
    1.29 +        ".alias bottom_row %i\n\n"
    1.30 +        ) % (scenery_rows, extra_rows,
    1.31 +             top_char_row, top_monster_row, top_row,
    1.32 +             bottom_char_row, bottom_monster_row, bottom_row)
    1.33 +    
    1.34      # Assemble the main game code and loader code.
    1.35      
    1.36      open("constants.oph", "w").write(constants_oph)

     2.1 --- a/code.oph	Fri Mar 21 22:14:42 2014 +0100
     2.2 +++ b/code.oph	Fri Mar 21 22:51:54 2014 +0100
     2.3 @@ -339,7 +339,7 @@
     2.4      bne check_beneath_fall
     2.5      
     2.6      lda player_y
     2.7 -    cmp #20                         ; The last visible row is 22 and the top of
     2.8 +    cmp #bottom_char_row            ; The last visible row is 22 and the top of
     2.9      bcs check_beneath_demise_exit   ; the character is two rows above that.
    2.10  
    2.11      adc #3
    2.12 @@ -411,10 +411,10 @@
    2.13                      ; returns C set if tile found or C clear if not
    2.14  
    2.15      lda $81         ; For y positions less than 7 do not check the corresponding
    2.16 -    cmp #7          ; row since there are no level spans in these rows.
    2.17 +    cmp #extra_rows ; row since there are no level spans in these rows.
    2.18      bcc check_tile_exit
    2.19  
    2.20 -    sbc #7
    2.21 +    sbc #extra_rows
    2.22      clc
    2.23  
    2.24      tax                       ; Transfer the y coordinate to the X register.

     3.1 --- a/monsters.oph	Fri Mar 21 22:14:42 2014 +0100
     3.2 +++ b/monsters.oph	Fri Mar 21 22:51:54 2014 +0100
     3.3 @@ -537,7 +537,7 @@
     3.4      move_monster_down:
     3.5  
     3.6      lda $89                     ; Recover the y offset.
     3.7 -    cmp #23
     3.8 +    cmp #bottom_monster_row
     3.9      beq move_monsters_change_direction
    3.10  
    3.11          dey                     ; Select the y offset.