Jet Set Willy: Routine at 36796

| Routines

36796: Move Willy (3)

Used by the routines at 36307 and 36564. This routine moves Willy left or right if necessary.
36796 | LD A,(34256) | Pick up Willy's direction and movement flags from 34256
36799 | AND 2 | Is Willy moving left or right?
36801 | RET Z | Return if not
36802 | LD A,(34262) | Pick up the rope status indicator from 34262
36805 | DEC A | Is Willy on a rope?
36806 | BIT 7,A
36808 | RET Z | Return if so (Willy's movement along a rope is handled at 37726)
36809 | LD A,(34256) | Pick up Willy's direction and movement flags from 34256
36812 | AND 1 | Is Willy facing right?
36814 | JP Z,36930 | Jump if so
Willy is moving left.
36817 | LD A,(34258) | Pick up Willy's animation frame from 34258
36820 | OR A | Is it 0?
36821 | JR Z,36828 | If so, jump to move Willy's sprite left across a cell boundary
36823 | DEC A | Decrement Willy's animation frame at 34258
36824 | LD (34258),A
36827 | RET |
Willy's sprite is moving left across a cell boundary. In the comments that follow, (x,y) refers to the coordinates of the top-left cell currently occupied by Willy's sprite.
36828 | LD A,(34257) | Pick up the airborne status indicator from 34257
36831 | LD BC,0 | Prepare BC for later addition
36834 | CP 0 | Is Willy jumping?
36836 | JR NZ,36874 | Jump if so
36838 | LD HL,(34259) | Collect Willy's attribute buffer coordinates from 34259
36841 | LD BC,0 | Prepare BC for later addition (again, redundantly)
36844 | LD A,(32986) | Pick up the direction byte of the ramp definition for the current room from 32986
36847 | DEC A | Now A=31 if the ramp goes up to the left, or 65 if it goes up to the right
36848 | OR 161
36850 | XOR 224
36852 | LD E,A | Point HL at the cell at (x-1,y+1) if the ramp goes up to the left, or at the cell at (x+1,y+2) if the ramp goes up to the right
36853 | LD D,0
36855 | ADD HL,DE
36856 | LD A,(32964) | Pick up the attribute byte of the ramp tile for the current room from 32964
36859 | CP (HL) | Is there a ramp tile in the cell pointed to by HL?
36860 | JR NZ,36874 | Jump if not
36862 | LD BC,32 | Prepare BC for later addition
36865 | LD A,(32986) | Pick up the direction byte of the ramp definition for the current room from 32986
36868 | OR A | Does the ramp go up to the right?
36869 | JR NZ,36874 | Jump if so
36871 | LD BC,65504 | BC=-32 (the ramp goes up to the left)
36874 | LD HL,(34259) | Collect Willy's attribute buffer coordinates from 34259
36877 | LD A,L | Is Willy's screen x-coordinate 0 (on the far left)?
36878 | AND 31
36880 | JP Z,38026 | If so, move Willy into the room to the left
36883 | ADD HL,BC | Point HL at the cell at (x-1,y+1), or at the cell at (x-1,y) if Willy is on or about to step onto a ramp that goes up to the left, or at the cell at (x-1,y+2) if Willy is walking down a ramp
36884 | DEC HL
36885 | LD DE,32
36888 | ADD HL,DE
36889 | LD A,(32946) | Pick up the attribute byte of the wall tile for the current room from 32946
36892 | CP (HL) | Is there a wall tile in the cell pointed to by HL?
36893 | RET Z | Return if so without moving Willy (his path is blocked)
36894 | LD A,(34255) | Pick up Willy's y-coordinate (Y) from 34255
36897 | SRA C | Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16 (if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp that goes up to the left); this will be Willy's new y-coordinate
36899 | ADD A,C
36900 | LD B,A
36901 | AND 15 | Is Willy at a point in a jump (left) where his sprite occupies three rows of cells?
36903 | JR Z,36914 | Jump if not (Willy's sprite is cell-aligned)
36905 | LD A,(32946) | Pick up the attribute byte of the wall tile for the current room from 32946
36908 | ADD HL,DE | Point HL at the cell at (x-1,y+2)
36909 | CP (HL) | Is there a wall tile there?
36910 | RET Z | Return if so without moving Willy (his path is blocked)
36911 | OR A | Point HL at the cell at (x-1,y+1)
36912 | SBC HL,DE
36914 | OR A | Point HL at the cell at (x-1,y), or at the cell at (x-1,y-1) if Willy is on or about to step onto a ramp that goes up to the left, or at the cell at (x-1,y+1) if Willy is walking down a ramp
36915 | SBC HL,DE
36917 | LD (34259),HL | Save Willy's new attribute buffer coordinates (in HL) at 34259
36920 | LD A,B | Save Willy's new y-coordinate at 34255
36921 | LD (34255),A
36924 | LD A,3 | Change Willy's animation frame at 34258 from 0 to 3
36926 | LD (34258),A
36929 | RET |
Willy is moving right.
36930 | LD A,(34258) | Pick up Willy's animation frame from 34258
36933 | CP 3 | Is it 3?
36935 | JR Z,36942 | If so, jump to move Willy's sprite right across a cell boundary
36937 | INC A | Increment Willy's animation frame at 34258
36938 | LD (34258),A
36941 | RET |
Willy's sprite is moving right across a cell boundary. In the comments that follow, (x,y) refers to the coordinates of the top-left cell currently occupied by Willy's sprite.
36942 | LD A,(34257) | Pick up the airborne status indicator from 34257
36945 | LD BC,0 | Prepare BC for later addition
36948 | OR A | Is Willy jumping?
36949 | JR NZ,36984 | Jump if so
36951 | LD HL,(34259) | Collect Willy's attribute buffer coordinates from 34259
36954 | LD A,(32986) | Pick up the direction byte of the ramp definition for the current room from 32986
36957 | DEC A | Now A=64 if the ramp goes up to the left, or 34 if it goes up to the right
36958 | OR 157
36960 | XOR 191
36962 | LD E,A | Point HL at the cell at (x,y+2) if the ramp goes up to the left, or at the cell at (x+2,y+1) if the ramp goes up to the right
36963 | LD D,0
36965 | ADD HL,DE
36966 | LD A,(32964) | Pick up the attribute byte of the ramp tile for the current room from 32964
36969 | CP (HL) | Is there a ramp tile in the cell pointed to by HL?
36970 | JR NZ,36984 | Jump if not
36972 | LD BC,32 | Prepare BC for later addition
36975 | LD A,(32986) | Pick up the direction byte of the ramp definition for the current room from 32986
36978 | OR A | Does the ramp go up to the left?
36979 | JR Z,36984 | Jump if so
36981 | LD BC,65504 | BC=-32 (the ramp goes up to the right)
36984 | LD HL,(34259) | Collect Willy's attribute buffer coordinates from 34259
36987 | ADD HL,BC | Point HL at the cell at (x+2,y), or at the cell at (x+2,y+1) if Willy is walking down a ramp, or at the cell at (x+2,y-1) if Willy is on or about to step onto a ramp that goes up to the right
36988 | INC HL
36989 | INC HL
36990 | LD A,L | Is Willy's screen x-coordinate 30 (on the far right)?
36991 | AND 31
36993 | JP Z,38046 | If so, move Willy into the room on the right
36996 | LD DE,32 | Prepare DE for addition
36999 | LD A,(32946) | Pick up the attribute byte of the wall tile for the current room from 32946
37002 | ADD HL,DE | Point HL at the cell at (x+2,y+1), or at the cell at (x+2,y+2) if Willy is walking down a ramp, or at the cell at (x+2,y) if Willy is on or about to step onto a ramp that goes up to the right
37003 | CP (HL) | Is there a wall tile in the cell pointed to by HL?
37004 | RET Z | Return if so without moving Willy (his path is blocked)
37005 | LD A,(34255) | Pick up Willy's y-coordinate (Y) from 34255
37008 | SRA C | Now B=Y (if Willy is neither on nor about to step onto a ramp), or Y+16 (if Willy is walking down a ramp), or Y-16 (if Willy is on or about to step onto a ramp that goes up to the right); this will be Willy's new y-coordinate
37010 | ADD A,C
37011 | LD B,A
37012 | AND 15 | Is Willy at a point in a jump (right) where his sprite occupies three rows of cells?
37014 | JR Z,37025 | Jump if not (Willy's sprite is cell-aligned)
37016 | LD A,(32946) | Pick up the attribute byte of the wall tile for the current room from 32946
37019 | ADD HL,DE | Point HL at the cell at (x+2,y+2)
37020 | CP (HL) | Is there a wall tile there?
37021 | RET Z | Return if so without moving Willy (his path is blocked)
37022 | OR A | Point HL at the cell at (x+2,y+1)
37023 | SBC HL,DE
37025 | LD A,(32946) | Pick up the attribute byte of the wall tile for the current room from 32946
37028 | OR A | Point HL at the cell at (x+2,y), or at the cell at (x+2,y+1) if Willy is walking down a ramp, or at the cell at (x+2,y-1) if Willy is on or about to step onto a ramp that goes up to the right
37029 | SBC HL,DE
37031 | CP (HL) | Is there a wall tile in the cell pointed to by HL?
37032 | RET Z | Return if so without moving Willy (his path is blocked)
37033 | DEC HL | Point HL at the cell at (x+1,y), or at the cell at (x+1,y+1) if Willy is walking down a ramp, or at the cell at (x+1,y-1) if Willy is on or about to step onto a ramp that goes up to the right
37034 | LD (34259),HL | Save Willy's new attribute buffer coordinates (in HL) at 34259
37037 | XOR A | Change Willy's animation frame at 34258 from 3 to 0
37038 | LD (34258),A
37041 | LD A,B | Save Willy's new y-coordinate at 34255
37042 | LD (34255),A
37045 | RET |