Sabre Wulf: Routine at 42708

42708: Change Orchid Stage

Used by the routine at HandlerOrchid.

Called when the timer of an orchid has run out. Every other frame the growth stage of the orchid (the lowest three bits of the sprite ID) is moved on by one. Whether it grows or shrinks depends on bit 3 of IX+2. When it has finished growing the timer is set to 16 and when it has finished shrinking a new colour is chosen and the timer is set to a random value between 128 and 191.

Input
IX	Actor record of the orchid

ChangeOrchidStage

42708

LD A,(38547)

Fetch the low byte of the game timer from GameTimer.

42711

AND %00000001

Keep only bit 0.

42713

JR NZ,HandlerOrchid_Draw

Jump to HandlerOrchid_Draw to just display the orchid if bit 0 is set.

42715

LD A,(IX+2)

Fetch the direction of growth of the orchid.

42718

AND A

Set the flags.

42719

JR Z,GrowOrchid

Jump to GrowOrchid if the orchid is growing.

The orchid is shrinking.

42721

DEC (IX+0)

Move the orchid back to the previous stage of growth.

42724

LD A,(IX+0)

Fetch the sprite ID of the orchid.

42727

AND %00000111

Keep only bits 0-2.

42729

JR NZ,HandlerOrchid_Draw

Jump to HandlerOrchid_Draw if the orchid has not finished shrinking.

The orchid has gone, so choose a new colour for the next time.

42731

LD A,(23672)

Fetch the low byte of FRAMES.

42734

AND %00001111

Keep only bits 0-3.

42736

LD L,A

Stash the colour index in L.

42737

LD H,0

Clear H.

42739

LD BC,42749

Point BC at the table of orchid colours at OrchidColour.

42742

ADD HL,BC

Add the table address to get the address of the colour.

42743

LD A,(HL)

Fetch the colour from the table.

42744

LD (IX+5),A

Set the colour of the orchid.

42747

JR GrowOrchid_Swap

Jump to GrowOrchid_Swap to swap the direction of growth.