| Routines

7C18: Move a character looking for ERIC to the midstride position

Continues from 7BA0. Moves the character looking for ERIC to the midstride position in the appropriate direction.
Input
A | 1 if the character's going upstairs, 2 if going down
BC | 0000
DE | 0000
H | Number of the character looking for ERIC (0xA1, 0xA3-0xA6)
L | 0x60
The main entry point is used when the character is on a staircase.
7C18 | INC B | B=1
7C19 | DEC A | Is the chaser going downstairs?
7C1A | JR NZ,$7C1E | Jump if so
7C1C | DEC B | B=0
7C1D | DEC D | D=-1
7C1E | INC C | C=1
7C1F | BIT 7,(HL) | Is the chaser facing right?
7C21 | JR NZ,$7C25 | Jump if so
7C23 | DEC C | C=-1
7C24 | DEC C
This entry point is used by the routine at 7BA0 when the character looking for ERIC is not on a staircase; in this case B=D=E=0, and C=-1 if the chaser is to ERIC's left, or 1 if he is to ERIC's right.
7C25 | LD L,$6B | C=-1 if the chaser is to ERIC's left, or 1 if to his right; B=1 if the chaser is going downstairs, 0 otherwise; place these values into bytes 0x6B and 0x6C of the chaser's buffer
7C27 | LD (HL),C
7C28 | INC L
7C29 | LD (HL),B
7C2A | LD L,$69 | Change the interruptible subcommand routine address in bytes 0x69 and 0x6A of the chaser's buffer from 7BA0 to 7BFB
7C2C | LD (HL),$FB
7C2E | PUSH DE | Save the x- and y-coordinate increments for the chaser's next move
7C2F | CALL $6214 | Update the SRB for the chaser's current location
7C32 | INC A | A=chaser's next animatory state (midstride)
7C33 | LD L,A | Store this in L briefly
7C34 | POP BC | Get the appropriate y- and x-coordinate increments for the chaser's move to the midstride position in BC
7C35 | LD A,B | Get the chaser's new y-coordinate in D (which is the same as his current y-coordinate unless he's going up a staircase)
7C36 | ADD A,D
7C37 | LD D,A
7C38 | LD A,C | Get the chaser's new x-coordinate in E (which is the same as his current x-coordinate, because C is always 0)
7C39 | ADD A,E
7C3A | LD E,A
7C3B | LD A,L | Restore the chaser's new animatory state to A
7C3C | JP $61B0 | Update the chaser's animatory state and location and update the SRB