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⌂ ∞ ▽ Elite on the 6502

Sprites

[Commodore 64 version]

 ELITE SPRITES



 ORG CODE%



       Name: SPRITE2                                                 [Show more]
       Type: Macro
   Category: Sprites
    Summary: Macro definition for a two-colour sprite pixel row

    Context: See this macro on its own page
 References: This macro is used as follows:
             * spritp uses SPRITE2




 This macro inserts three bytes of a two-colour sprite pixel row, with eight
 pixels per byte (i.e. eight pixels per character block).



 Arguments:

   pixel_row            A string containing a row of 24 pixels, where each pixel
                        is defined as follows:

                          * X denotes colour 1

                          * Anything else denotes colour 0



MACRO SPRITE2 pixel_row

 SPRITE2_BYTE MID$(pixel_row, 1, 8)
 SPRITE2_BYTE MID$(pixel_row, 9, 8)
 SPRITE2_BYTE MID$(pixel_row, 17, 8)

ENDMACRO



       Name: SPRITE2_BYTE                                            [Show more]
       Type: Macro
   Category: Sprites
    Summary: Macro definition for a two-colour sprite pixel byte

    Context: See this macro on its own page
 References: No direct references to this macro in this source file




 This macro inserts one byte of a two-colour sprite pixel row, with eight
 pixels per byte (i.e. eight pixels per character block).

 In BeebAsm, true statements evaluate to -1 while false statements evaluate to
 0 (just as in BBC BASIC), so this statement:

   bit7 = -(ASC(MID$(pixel_byte, 1, 1)) = ASC("X")) << 7

 does the same as this longer statement:

   IF ASC(MID$(pixel_byte, 1, 1)) = ASC("X")
    bit7 = 1 << 7
   ELSE
    bit7 = 0
   ENDIF

 In other words, bit7 gets set to 1 << 7 (i.e. %10000000) if character 1 of
 pixel_byte is "X", otherwise it gets set to 0.



 Arguments:

   pixel_byte           A string containing a row of 8 pixels, where each pixel
                        is defined as follows:

                          * "X" denotes colour 1

                          * Anything else (e.g. "." or "+") denotes colour 0



MACRO SPRITE2_BYTE pixel_byte

 bit7 = -(ASC(MID$(pixel_byte, 1, 1)) = ASC("X")) << 7
 bit6 = -(ASC(MID$(pixel_byte, 2, 1)) = ASC("X")) << 6
 bit5 = -(ASC(MID$(pixel_byte, 3, 1)) = ASC("X")) << 5
 bit4 = -(ASC(MID$(pixel_byte, 4, 1)) = ASC("X")) << 4
 bit3 = -(ASC(MID$(pixel_byte, 5, 1)) = ASC("X")) << 3
 bit2 = -(ASC(MID$(pixel_byte, 6, 1)) = ASC("X")) << 2
 bit1 = -(ASC(MID$(pixel_byte, 7, 1)) = ASC("X")) << 1
 bit0 = -(ASC(MID$(pixel_byte, 8, 1)) = ASC("X")) << 0

 EQUB bit7 + bit6 + bit5 + bit4 + bit3 + bit2 + bit1 + bit0

ENDMACRO



       Name: SPRITE4                                                 [Show more]
       Type: Macro
   Category: Sprites
    Summary: Macro definition for a four-colour sprite pixel row

    Context: See this macro on its own page
 References: This macro is used as follows:
             * spritp uses SPRITE4




 This macro inserts three bytes of a four-colour sprite pixel row, with four
 pixels per byte (i.e. four pixels per character block).



 Arguments:

   pixel_row            A string containing a row of 12 pixels, where each pixel
                        is defined as follows:

                          * "/" denotes colour 1

                          * "*" denotes colour 2

                          * "@" denotes colour 3

                          * Anything else (e.g. ".") denotes colour 0



MACRO SPRITE4 pixel_row

 SPRITE4_BYTE MID$(pixel_row, 1, 4)
 SPRITE4_BYTE MID$(pixel_row, 5, 4)
 SPRITE4_BYTE MID$(pixel_row, 9, 4)

ENDMACRO



       Name: SPRITE4_BYTE                                            [Show more]
       Type: Macro
   Category: Sprites
    Summary: Macro definition for a four-colour sprite pixel byte

    Context: See this macro on its own page
 References: No direct references to this macro in this source file




 This macro inserts one byte of a four-colour sprite pixel row, with four
 pixels per byte (i.e. four pixels per character block).

 In BeebAsm, true statements evaluate to -1 while false statements evaluate to
 0 (just as in BBC BASIC), so this statement:

   bit67_1 = (%01 * -(ASC(MID$(pixel_byte, 1, 1)) = ASC("/"))) << 6

 does the same as this longer statement:

   IF ASC(MID$(pixel_byte, 1, 1)) = ASC("/")
    bit67_1 = %01 << 6
   ELSE
    bit67_1 = 0
   ENDIF

 In other words, bit67_1 gets set to %01 << 6 (i.e. %01000000) if character 1
 of pixel_byte is "/", otherwise it gets set to 0.



 Arguments:

   pixel_byte           A string containing a row of 4 pixels, where each pixel
                        is defined as follows:

                          * "/" denotes colour 1

                          * "*" denotes colour 2

                          * "@" denotes colour 3

                          * Anything else (e.g. ".") denotes colour 0



MACRO SPRITE4_BYTE pixel_byte

 bit67_1 = (%01 * -(ASC(MID$(pixel_byte, 1, 1)) = ASC("/"))) << 6
 bit67_2 = (%10 * -(ASC(MID$(pixel_byte, 1, 1)) = ASC("*"))) << 6
 bit67_3 = (%11 * -(ASC(MID$(pixel_byte, 1, 1)) = ASC("@"))) << 6

 bit45_1 = (%01 * -(ASC(MID$(pixel_byte, 2, 1)) = ASC("/"))) << 4
 bit45_2 = (%10 * -(ASC(MID$(pixel_byte, 2, 1)) = ASC("*"))) << 4
 bit45_3 = (%11 * -(ASC(MID$(pixel_byte, 2, 1)) = ASC("@"))) << 4

 bit23_1 = (%01 * -(ASC(MID$(pixel_byte, 3, 1)) = ASC("/"))) << 2
 bit23_2 = (%10 * -(ASC(MID$(pixel_byte, 3, 1)) = ASC("*"))) << 2
 bit23_3 = (%11 * -(ASC(MID$(pixel_byte, 3, 1)) = ASC("@"))) << 2

 bit01_1 = (%01 * -(ASC(MID$(pixel_byte, 4, 1)) = ASC("/"))) << 0
 bit01_2 = (%10 * -(ASC(MID$(pixel_byte, 4, 1)) = ASC("*"))) << 0
 bit01_3 = (%11 * -(ASC(MID$(pixel_byte, 4, 1)) = ASC("@"))) << 0

 bit67 = bit67_1 + bit67_2 + bit67_3
 bit45 = bit45_1 + bit45_2 + bit45_3
 bit23 = bit23_1 + bit23_2 + bit23_3
 bit01 = bit01_1 + bit01_2 + bit01_3

 EQUB bit67 + bit45 + bit23 + bit01

ENDMACRO



       Name: spritp                                                  [Show more]
       Type: Variable
   Category: Sprites
    Summary: Sprite definitions for four laser sights, the explosion sprite and
             two Trumbles

    Context: See this variable on its own page
 References: No direct references to this variable in this source file




.spritp

 SPRITE2 "........................"     ; The laser sights for a pulse laser
 SPRITE2 "........................"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "..XXXXX....+....XXXXX..."
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "........................"
 SPRITE2 "........................"

 EQUB $3A               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE2 "........................"     ; The laser sights for a beam laser
 SPRITE2 "........................"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 ".....XXXXXXXXXXXXX......"
 SPRITE2 ".....X...........X......"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "...........+............"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 ".....X...........X......"
 SPRITE2 ".....XXXXXXXXXXXXX......"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "...........X............"
 SPRITE2 "........................"
 SPRITE2 "........................"

 EQUB $31               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE2 "........................"     ; The laser sights for a military laser
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........XXXXXXX........."
 SPRITE2 ".........X...X.........."
 SPRITE2 "..........X.X..........."
 SPRITE2 "...........X............"
 SPRITE2 "..XX...............XX..."
 SPRITE2 "..X.X.............X.X..."
 SPRITE2 "..X..X...........X..X..."
 SPRITE2 "..X...X....+....X...X..."
 SPRITE2 "..X..X...........X..X..."
 SPRITE2 "..X.X.............X.X..."
 SPRITE2 "..XX...............XX..."
 SPRITE2 "...........X............"
 SPRITE2 "..........X.X..........."
 SPRITE2 ".........X...X.........."
 SPRITE2 "........XXXXXXX........."
 SPRITE2 "........................"
 SPRITE2 "........................"
 SPRITE2 "........................"

 EQUB $45               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE2 "..XXXXXXXXXXXXXXXXXXX..."     ; The laser sights for a mining laser
 SPRITE2 "..X........X........X..."
 SPRITE2 "..X.......XXX.......X..."
 SPRITE2 "....X......X......X....."
 SPRITE2 "XX...X....XXX....X...XX."
 SPRITE2 "X.....X....X....X.....X."
 SPRITE2 "X......X..XXX..X......X."
 SPRITE2 "X..........X..........X."
 SPRITE2 "X........XXXXX........X."
 SPRITE2 "X.X..XX..X...X..XX..X.X."
 SPRITE2 "XXXXXX.....X.....XXXXXX."
 SPRITE2 "X.X..XX..X...X..XX..X.X."
 SPRITE2 "X........XXXXX........X."
 SPRITE2 "X..........X..........X."
 SPRITE2 "X......X..XXX..X......X."
 SPRITE2 "X.....X....X....X.....X."
 SPRITE2 "XX...X....XXX....X...XX."
 SPRITE2 "....X......X......X....."
 SPRITE2 "..X.......XXX.......X..."
 SPRITE2 "..X........X........X..."
 SPRITE2 "..XXXXXXXXXXXXXXXXXXX..."

 EQUB $A3               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE2 "........................"     ; The explosion cloud sprite
 SPRITE2 ".........X....XX........"
 SPRITE2 "...X....XX..X...X......."
 SPRITE2 ".....X....XX...XXX......"
 SPRITE2 "...X..XX.....X..XX..X..."
 SPRITE2 "....X.....X.XX....X..X.."
 SPRITE2 ".X.XX..X..X.XX.XXX..XX.."
 SPRITE2 "...X..XX.X.X.XX...XXX..."
 SPRITE2 "XX..X.X..XX.XXX....X.XX."
 SPRITE2 "....XXX..XX.XX.XX...X.XX"
 SPRITE2 "..X.....XX.XX.XXX..XX..."
 SPRITE2 ".....XX.XX..X.XXX.XX...."
 SPRITE2 "..X...XXX.X.X..XX...X.X."
 SPRITE2 "X...XXX..XX.XX.XX...X.XX"
 SPRITE2 "...X..XX..X..X..XX..X..."
 SPRITE2 "..XX..XX..X.XX.XX..X.X.."
 SPRITE2 "....X....XX...XXX...X..."
 SPRITE2 "...XX........X....X....."
 SPRITE2 "...XX...XX....X.....XX.."
 SPRITE2 "........XX..X...X......."
 SPRITE2 ".............XX........."

 EQUB $44               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE4 ".....***...."     ; A Trumble looking to the right
 SPRITE4 "..*.*****..."
 SPRITE4 "..***/*/**.."
 SPRITE4 ".**********."
 SPRITE4 "..**********"
 SPRITE4 ".*/***/****."
 SPRITE4 "****/*******"
 SPRITE4 ".********/*."
 SPRITE4 "************"
 SPRITE4 "************"
 SPRITE4 ".**********."
 SPRITE4 "***@@***@@**"
 SPRITE4 "**@@@@*@@@@*"
 SPRITE4 "**@@*@*@@*@*"
 SPRITE4 "***@@***@@**"
 SPRITE4 ".**********."
 SPRITE4 "..********.."
 SPRITE4 "...******..."
 SPRITE4 "....*//*...."
 SPRITE4 ".....//....."
 SPRITE4 "............"

 EQUB $44               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process

 SPRITE4 "............"     ; A Trumble looking to the left
 SPRITE4 "............"
 SPRITE4 "......**...."
 SPRITE4 "..**.****..."
 SPRITE4 ".*****/***.."
 SPRITE4 ".**********."
 SPRITE4 "****/******."
 SPRITE4 ".**********."
 SPRITE4 "************"
 SPRITE4 "************"
 SPRITE4 ".**********."
 SPRITE4 "***@@***@@**"
 SPRITE4 "**@@@@*@@@@*"
 SPRITE4 "**@*@@*@*@@*"
 SPRITE4 "***@@***@@**"
 SPRITE4 ".**********."
 SPRITE4 "..********.."
 SPRITE4 ".../****/..."
 SPRITE4 "....*//*...."
 SPRITE4 ".....//....."
 SPRITE4 "............"

 EQUB $54               ; This byte appears to be unused and just contains
                        ; random workspace noise left over from the BBC Micro
                        ; assembly process


 Save SPRITE.bin



 PRINT "P% = ", ~P%
 PRINT "S.C.SPRITE ", ~CODE%, " +1C0"
 SAVE "3-assembled-output/SPRITE.bin", CODE%, P%, LOAD%