Skool Daze: Routine at 7C18

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