Routines
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35805: Move Willy (2)
Used by the routine at 35515. This routine checks the keyboard and joystick, and moves Willy left or right if necessary.
Input
HL Attribute buffer address of the left-hand cell below Willy's sprite
35805 LD A,(32875) Pick up the airborne status indicator from 32875
35808 CP 12 Has Willy just landed after falling from too great a height?
35810 JP NC,36102 If so, kill him
35813 LD E,255 Initialise E to 255 (all bits set); it will be used to hold keyboard and joystick readings
35815 XOR A Reset the airborne status indicator at 32875 (Willy has landed safely)
35816 LD (32875),A
35819 LD A,(32836) Pick up the attribute byte of the conveyor tile for the current cavern from 32836
35822 CP (HL) Does the attribute byte of the left-hand cell below Willy's sprite match that of the conveyor tile?
35823 JR Z,35829 Jump if so
35825 INC HL Point HL at the right-hand cell below Willy's sprite
35826 CP (HL) Does the attribute byte of the right-hand cell below Willy's sprite match that of the conveyor tile?
35827 JR NZ,35835 Jump if not
35829 LD A,(32879) Pick up the direction byte of the conveyor definition from 32879 (0=left, 1=right)
35832 SUB 3 Now E=253 (bit 1 reset) if the conveyor is moving left, or 254 (bit 0 reset) if it's moving right
35834 LD E,A
35835 LD BC,57342 Read keys P-O-I-U-Y (right, left, right, left, right) into bits 0-4 of A
35838 IN A,(C)
35840 AND 31 Set bit 5 and reset bits 6 and 7
35842 OR 32
35844 AND E Reset bit 0 if the conveyor is moving right, or bit 1 if it's moving left
35845 LD E,A Save the result in E
35846 LD BC,64510 Read keys Q-W-E-R-T (left, right, left, right, left) into bits 0-4 of A
35849 IN A,(C)
35851 AND 31 Keep only bits 0-4, shift them into bits 1-5, and set bit 0
35853 RLC A
35855 OR 1
35857 AND E Merge this keyboard reading into bits 1-5 of E
35858 LD E,A
35859 LD B,247 Read keys 1-2-3-4-5 ('5' is left) into bits 0-4 of A
35861 IN A,(C)
35863 RRCA Rotate the result right and set bits 0-2 and 4-7; this ignores every key except '5' (left)
35864 OR 247
35866 AND E Merge this reading of the '5' key into bit 3 of E
35867 LD E,A
35868 LD B,239 Read keys 0-9-8-7-6 ('8' is right) into bits 0-4 of A
35870 IN A,(C)
35872 OR 251 Set bits 0, 1 and 3-7; this ignores every key except '8' (right)
35874 AND E Merge this reading of the '8' key into bit 2 of E
35875 LD E,A
35876 LD A,(33881) Collect the Kempston joystick indicator from 33881
35879 OR A Is the joystick connected?
35880 JR Z,35892 Jump if not
35882 LD BC,31 Collect input from the joystick
35885 IN A,(C)
35887 AND 3 Keep only bits 0 (right) and 1 (left) and flip them
35889 CPL
35890 AND E Merge this reading of the joystick right and left buttons into bits 0 and 1 of E
35891 LD E,A
At this point, bits 0-5 in E indicate the direction in which Willy is being moved or trying to move. If bit 0, 2 or 4 is reset, Willy is being moved or trying to move right; if bit 1, 3 or 5 is reset, Willy is being moved or trying to move left.
35892 LD C,0 Initialise C to 0 (no movement)
35894 LD A,E Copy the movement bits into A
35895 AND 42 Keep only bits 1, 3 and 5 (the 'left' bits)
35897 CP 42 Are any of these bits reset?
35899 JR Z,35903 Jump if not
35901 LD C,4 Set bit 2 of C: Willy is moving left
35903 LD A,E Copy the movement bits into A
35904 AND 21 Keep only bits 0, 2 and 4 (the 'right' bits)
35906 CP 21 Are any of these bits reset?
35908 JR Z,35912 Jump if not
35910 SET 3,C Set bit 3 of C: Willy is moving right
35912 LD A,(32874) Pick up Willy's direction and movement flags from 32874
35915 ADD A,C Point HL at the entry in the left-right movement table at 33800 that corresponds to the direction Willy is facing, and the direction in which he is being moved or trying to move
35916 LD C,A
35917 LD B,0
35919 LD HL,33800
35923 LD A,(HL) Update Willy's direction and movement flags at 32874 with the entry from the left-right movement table
35924 LD (32874),A
That is left-right movement taken care of. Now check the jump keys.
35927 LD BC,32510 Read keys SHIFT-Z-X-C-V and B-N-M-SS-SPACE
35930 IN A,(C)
35932 AND 31 Are any of these keys being pressed?
35934 CP 31
35936 JR NZ,35963 Jump if so
35938 LD B,239 Read keys 0-9-8-7-6 into bits 0-4 of A
35940 IN A,(C)
35942 AND 9 Keep only bits 0 (the '0' key) and 3 (the '7' key)
35944 CP 9 Is '0' or '7' being pressed?
35946 JR NZ,35963 Jump if so
35948 LD A,(33881) Collect the Kempston joystick indicator from 33881
35951 OR A Is the joystick connected?
35952 JR Z,35971 Jump if not
35954 LD BC,31 Collect input from the joystick
35957 IN A,(C)
35959 BIT 4,A Is the fire button being pressed?
35961 JR Z,35971 Jump if not
A jump key or the fire button is being pressed. Time to make Willy jump.
35963 XOR A Initialise the jumping animation counter at 32878
35964 LD (32878),A
35967 INC A Set the airborne status indicator at 32875 to 1: Willy is jumping
35968 LD (32875),A
This entry point is used by the routine at 35515.
35971 LD A,(32874) Pick up Willy's direction and movement flags from 32874
35974 AND 2 Is Willy moving?
35976 RET Z Return if not
35977 LD A,(32874) Pick up Willy's direction and movement flags from 32874
35980 AND 1 Is Willy facing right?
35982 JP Z,36042 Jump if so
Willy is moving left.
35985 LD A,(32873) Pick up Willy's animation frame from 32873
35988 OR A Is it 0?
35989 JR Z,35996 If so, jump to move Willy's sprite left across a cell boundary
35991 DEC A Decrement Willy's animation frame at 32873
35992 LD (32873),A
35995 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.
35996 LD HL,(32876) Collect Willy's attribute buffer coordinates from 32876
35999 DEC HL Point HL at the cell at (x-1,y+1)
36000 LD DE,32
36004 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36007 CP (HL) Is there a wall tile in the cell pointed to by HL?
36008 RET Z Return if so without moving Willy (his path is blocked)
36009 LD A,(32872) Pick up Willy's y-coordinate from 32872
36012 AND 15 Does Willy's sprite currently occupy only two rows of cells?
36014 JR Z,36025 Jump if so
36016 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36019 ADD HL,DE Point HL at the cell at (x-1,y+2)
36020 CP (HL) Is there a wall tile in the cell pointed to by HL?
36021 RET Z Return if so without moving Willy (his path is blocked)
36022 OR A Clear the carry flag for subtraction
36023 SBC HL,DE Point HL at the cell at (x-1,y+1)
36025 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36028 OR A Clear the carry flag for subtraction
36029 SBC HL,DE Point HL at the cell at (x-1,y)
36031 CP (HL) Is there a wall tile in the cell pointed to by HL?
36032 RET Z Return if so without moving Willy (his path is blocked)
36033 LD (32876),HL Save Willy's new attribute buffer coordinates (in HL) at 32876
36036 LD A,3 Change Willy's animation frame at 32873 from 0 to 3
36038 LD (32873),A
36041 RET
Willy is moving right.
36042 LD A,(32873) Pick up Willy's animation frame from 32873
36045 CP 3 Is it 3?
36047 JR Z,36054 If so, jump to move Willy's sprite right across a cell boundary
36049 INC A Increment Willy's animation frame at 32873
36050 LD (32873),A
36053 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.
36054 LD HL,(32876) Collect Willy's attribute buffer coordinates from 32876
36057 INC HL Point HL at the cell at (x+2,y)
36058 INC HL
36059 LD DE,32 Prepare DE for addition
36062 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36065 ADD HL,DE Point HL at the cell at (x+2,y+1)
36066 CP (HL) Is there a wall tile in the cell pointed to by HL?
36067 RET Z Return if so without moving Willy (his path is blocked)
36068 LD A,(32872) Pick up Willy's y-coordinate from 32872
36071 AND 15 Does Willy's sprite currently occupy only two rows of cells?
36073 JR Z,36084 Jump if so
36075 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36078 ADD HL,DE Point HL at the cell at (x+2,y+2)
36079 CP (HL) Is there a wall tile in the cell pointed to by HL?
36080 RET Z Return if so without moving Willy (his path is blocked)
36081 OR A Clear the carry flag for subtraction
36082 SBC HL,DE Point HL at the cell at (x+2,y+1)
36084 LD A,(32827) Pick up the attribute byte of the wall tile for the current cavern from 32827
36087 OR A Clear the carry flag for subtraction
36088 SBC HL,DE Point HL at the cell at (x+2,y)
36090 CP (HL) Is there a wall tile in the cell pointed to by HL?
36091 RET Z Return if so without moving Willy (his path is blocked)
36092 DEC HL Point HL at the cell at (x+1,y)
36093 LD (32876),HL Save Willy's new attribute buffer coordinates (in HL) at 32876
36096 XOR A Change Willy's animation frame at 32873 from 3 to 0
36097 LD (32873),A
36100 RET
 Prev: 35770 Up: Map Next: 36101