river-raid: Routine at 696B

696B: Initialize island state from terrain data

Called when terrain data indicates an island should appear. Looks up island parameters from data_islands table and stores them to state variables for use during island line rendering.

Input
A	Island index (upper 6 bits of terrain byte, will be divided by 4).

handle_island

696B

LD HL,$C600

Convert input to island table index and prepare lookup.

696E

LD DE,$0003

6971

SRL A

6973

SRL A

6975

OR A

6976

SBC HL,DE

locate_island_element

6978

ADD HL,DE

Locate island entry in data_islands (3 bytes per entry).

6979

DEC A

697A

JR NZ,$6977

697C

LD A,(HL)

Store island profile index and width offset to state.

697D

LD ($5EFA),A

6980

INC HL

6981

LD A,(HL)

6982

LD ($5EFB),A

6985

INC HL

6986

LD A,(HL)

Store extra byte and reset island line counter.

6987

LD ($5EFC),A

698A

LD A,$00

698C

LD ($5EFD),A

698F

RET