Knight Lore: Routine at B8DA

The bubbles rise out of the cauldron, cycling through four frames, and they are not solid on the way up (bit 1 of +7 is set, so the collision code ignores them). At height $A0 they hover, and every fourth frame they are replaced by a picture of the next object the wizard wants -- type 168 plus that object's number -- for one frame in every five: the picture, then 160, 161, 162 and 163, then the picture again.

If the player is Sabrewulf -- his legs are type 48 to 63 -- the bubbles turn hostile instead: they become types 164 to 167 (upd_164_to_167), solid, and still carry the deadly bits their starting record gave them.

They vanish while object record 2 is occupied, which is while an object has been dropped into the cauldron and is being taken. init_cauldron_bubbles puts them back once the record is free again.

The bubbles rise out of the cauldron, cycling through four frames, and they are not solid on the way up (bit 1 of +7 is set, so the collision code ignores them). At height $A0 they hover, and every fourth frame they are replaced by a picture of the next object the wizard wants -- type 168 plus that object's number -- for one frame in every five: the picture, then 160, 161, 162 and 163, then the picture again. If the player is Sabrewulf -- his legs are type 48 to 63 -- the bubbles turn hostile instead: they become types 164 to 167 (upd_164_to_167), solid, and still carry the deadly bits their starting record gave them. They vanish while object record 2 is occupied, which is while an object has been dropped into the cauldron and is being taken. init_cauldron_bubbles puts them back once the record is free again.
upd_160_to_163	B8DA	CALL adj_m4_m12	pixel offsets
	B8DD	LD A,($5C48)	an object is in the cauldron: vanish
	B8E0	AND A
	B8E1	JP NZ,upd_111
	B8E4	SET 1,(IX+$07)	not solid
	B8E8	CALL dec_dZ_and_update_XYZ	move; next of four frames
	B8EB	CALL next_graphic_no_mod_4	move; next of four frames
	B8EE	LD A,(IX+$03)	still below $A0: dZ = 2, so rise one unit
	B8F1	CP $A0
	B8F3	LD (IX+$0B),$02
	B8F7	JR C,bubbles_draw
	B8F9	LD (IX+$0B),$01	at the top: dZ = 1, so hover
	B8FD	LD A,($5C08)	the player is Sabrewulf
	B900	SUB $30
	B902	CP $10
	B904	JR C,bubbles_turn_hostile
	B906	LD A,(IX+$00)	only when the cycle comes back round to 160
	B909	AND $03
	B90B	JR NZ,bubbles_draw
	B90D	CALL ret_next_obj_required	show the object wanted: type 168 plus its number
	B910	LD A,(HL)
	B911	OR $A8
	B913	LD (IX+$00),A