alien: Routine at 40149

40149: ClearAlienArea

Clears the 19x20-character area of the ZX Spectrum display file and attribute RAM used by the alien body animation. Iterates 19 rows of 20 columns from DisplayFile, calling 31370 to zero each cell, then repeats for the attribute area at AttrFileOrigin.
40149	LD HL,16384	HL = DisplayFile: start of display file
40152	LD (31257),HL	store current screen cell address
40155	LD C,19	19 character rows
40157	LD B,20
40159	PUSH BC
40160	XOR A
40161	CALL 31370
40164	LD HL,31257
40167	INC (HL)
40168	POP BC
40169	DJNZ 40159
40171	LD DE,12
40174	LD HL,(31257)
40177	LD A,L
40178	CP 224
40180	JR C,40185
40182	LD DE,1804
40185	ADD HL,DE
40186	LD (31257),HL
40189	DEC C
40190	JR NZ,40157
40192	LD DE,12
40195	LD HL,22528
40198	LD C,19
40200	LD B,20
40202	LD (HL),4
40204	INC HL
40205	DJNZ 40202
40207	ADD HL,DE
40208	DEC C
40209	JR NZ,40200
40211	RET
LaunchGate: fixture 78 (Narcissus launch console). The launch is COUNTERMANDED (msg #28) unless every living crew member's room is 34 (Narcissus); then Jones must be aboard too (JonesRoom = 34, or the cat present in the shuttle strip cells) or msg #27 "BioUnit Jones not present" fires first.
40212	LD HL,29581	walk the +7 status column of all 7 crew
40215	LD DE,8
40218	LD B,7
40220	XOR A
40221	CP (HL)
40222	JR NZ,40235
40224	PUSH DE
40225	LD DE,65530
40228	ADD HL,DE
40229	POP DE
40230	LD A,(HL)
40231	CP 34
40233	JR NZ,40275
40235	ADD HL,DE
40236	DJNZ 40220
40238	LD A,(33706)
40241	CP 34
40243	JR Z,40281
40245	CP 255
40247	JR NZ,40270
40249	LD HL,29960
40252	LD B,2
40254	LD A,(HL)
40255	CP 255
40257	JR Z,40267
40259	CP 34
40261	JR Z,40281
40263	CP 128
40265	JR NC,40281
40267	INC HL
40268	DJNZ 40254
40270	LD A,27
40272	CALL 37176
40275	LD A,28
40277	CALL 37176
40280	RET
40281	LD B,75
40283	PUSH BC
40284	LD A,1
40286	LD (33699),A
40289	CALL 40319
40292	LD DE,12
40295	LD HL,22528
40298	LD C,19
40300	LD B,20
40302	LD A,(HL)
40303	XOR 64
40305	LD (HL),A
40306	INC HL
40307	DJNZ 40302
40309	ADD HL,DE
40310	DEC C
40311	JR NZ,40300
40313	POP BC
40314	DJNZ 40283
40316	JP 44159