mg-asm-analysis.txt

mg screen stuff...

Code for picking up items: 8fdb
don't act on p-bomb, min, missile, ration, ammo.
for weapons, hl = c520; for equipment, hl = c5a0 and a -= 8
hl[a-1] = 1: found object

41df: hl += 2*a
41e0: hl += a
41e5: de += a
41ea: jp (sp[2a])
4248: *** set pages 1, 2, 3 ***
424e: *** set pages 4, 5, 6 *** (store values at 0xf0f1 too)
426a: *** set pages 7, 8, 9 ***
4270: *** set pages a, b, c ***
4276: *** set pages d, e, f ***

42b4: *** de = de[a]
42d4: *** read nybble from hl[a] -> a *** {{{
	c=a
	hl += a / 2
	a=(hl)
	if c & 1:
		a >>=4
	a &= 0x0f
}}}

Palette stuff {{{
4ab5:	pages a,b,c
	a=6185[room]
	pages 4,5,6
	de=8cb4
	set palette hl[a]
	return 1,2,3

4acb: set palette for room (4,5,6:8b40 or special for no light/ir goggles) {{{
	hl = 8b40
	pages 4,5,6
	b = room
	if room == 0xfb:	# this room does not exist?!
		goto 4aff	# No goggles
	if room in (0xdc, 0xdd):	# Middle of dark corridor
		goto 4ae9
	if not 0x7b <= room <= 0x7e:	# Rest of dark corridor
		goto 4af4

4ae9:	*c135 (selected item) == 3 (light): goto 4af4
4af4:	*c135 (selected item) != 4 (goggl): goto 4aff
4aff:	No special lights
	read nybble from 8b40[room]
	set pages 4,5,6
	hl = 8bbe[a]
	set palette from hl:
		while True:
			a = *hl++
			if a == 0xff: return
			de = *hl++
			4e66: set palette data for color a to de (rb:g)
	return with pages 1,2,3
}}}

goggles: a = 0xa
dark: a = 0xb
normal: a = 456:8b40[room] (nybble)

4a92:
	set pages 4,5,6
	set_palette(0x8b0b)
	4a66 = 4248: set pages 1,2,3; return

4b09:
	set palette(hl[a])
	return pages 1,2,3


4ec4: *** Set palette from *hl *** (store values in vram at 0x.... too) {{{
	while True:
		a=*hl++
		if a == 0xff: return
		de = *hl++++
		call 4e66
}}}

4e66: *** Set single palette value *** {{{
	[0x99] = a
	[0x99] = 0x90	register 16: palette address
	[0x9a] = d	palette data
	[0x9a] = e	palette data
	hl = 0xf680 + 2 * a
	call 4d93	write to vram at hl
	[0x99] = d
	[0x99] = e
}}}
}}}

4d93: *** Prepare vdp for vram write at hl *** {{{
	[0x99] = (h >> 6) & 3
	[0x99] = 0x8e	register 14: top vram address bits
	[0x99] = l
	[0x99] = (h & 0x3f) | 40	write data to this address
}}}

4ed2: *** Wait for vdp command to complete ***

5011: vdp copy vram to vram {{{
	src: 0:h, a[6:7]:l
	dst: 0:d, a[5:4]:e
	cnt: 0:b, 0:c
	col: 0
	arg: 0
	cmd: 0x90 | a[3:0]	(vram copy; filter type)
}}}

4acb: set palette for room tiles
42bd: hl = 4*(a-1)
42d1: read nybble from hl[room]

4cf0: draw screen {{{
	4276: set d,e,f
	4e1b: clear screen with hmmv
	42b1 (de=0x6000): de = de[room]
	4c9a:
		ec06 = loop counter (8 blocks)
		ec00 = dest pointer
		ec04 = src pointer for block list
		a = 61f6[room] (nybble)
		de = 6274[a-1]
		ec02 = src pointer for block content
		a = *ec04
		*ec04 += 1
		hl = de + 16 * (a-1)
		copy hl->de (4x4)

in pages d,e,f
copy hl to de, de = e000, hl = 6a60
ec04 = hl = 6000[room] (word)
a = 61f6[room] (nybble)
ec02 = 6274[a-1]
hl = (ec02) + 16 * ((++ec04) - 1)
hl = 84b0
}}}

4935: write charset {{{
	42c4: ldir(src=4b13, dst=e700,cnt=8)
	426a: page 7,8,9
	a=nybble 6000[room]
	if a==c157: return
	4bbc:
		pages d,e,f
		42c4: ldir(src=4b13, dst=e700,cnt=8)
		524c(hl=b2bf,de=9048,b=4)	Write lift buttons.
	426a: page 7,8,9
	ix = 607e[a]
	3*:
		ix[0].7 ? ->skip
		49a7:
			ix[0].6 ? -> other stuff:
				b = last_b
				hl = 49df(a = ix[1])
				de = last_de
				5265: b*:
					hl'=e708
					527e (build character from hl)
					50b1(hl=e707, b=1): b*:
						8*:
							nybble-swap e707[0:4]->ec43[::-1]
							de += 8
						5087 (hl = 0xec40) (write char from hl to vram de)
						de += 4 with weird overflow (next character)
			b = ix[1]
			49df(a = ix[2]):
				hl = 8000 + (a & 0xe0) << 5 + (a & 0x1f) << 2
			de = hl
			hl = ix[3:4]
			524c: build b characters from hl to vram de
				for _ in range(b):
					hl' = e708
					527e: 8*
						e=*hl++
						d=*hl++
						c=*hl++
						4*:
							e=00000cde (bits 7 of all)
							d=e7
							c'=*de * 16
							e=00000cde (bits 6 of all)
							d=e7
							*hl'++ = c' | *de
					509c(hl = e708, b=1): b*
						5087: write character from hl to vram de
							8*:
								4d59(bc=4): write bc bytes to vram hl
									4d93: write to vram at hl
									4d51: a = b + (c != 0); b = c
									98 << *hl * bc
						de += 4 for next character
}}}

4b33: draw items
	4bcf:
		pages 7,8,9
		42c4: set palette
		draw boxes and mirorred boxes
		return 1,2,3
	pages 4,5,6
	42c7: set palette
	write characters (hl=a75d, de=b000, b=0x84)



5fa6:
	4a9d:
		(pages=1,2,3)
		hl=4aa3
		4ec4: set palette from *hl

41e5: de += a

store *(c450 + door - 1)
*(b046 + door - 1)

1 2  1 gas mask
2 41   elevator
3 5  4 courtyard prisoner
4 5  4 exit courtyard
5 5  4 doorsteek
6 45 4 exit building 1
7 5  4 petro gone
8 42 1 prisoner
9 3  2 smg
a 43 2 prisoner
b 41   elevator
c 2f f secret cell exit
d 7  6 north
e 7  6 ellen
f 4  3 shoot gunner
10 30 b uniform

2-9: need card 1-8, remains open
b (69)
d: jennifer (compass)
e: auto open at event (mg dead; big boss dead)
10: explode
2f: punch
30: explode
41: elevator
42-49: need card 1-8, auto close
81: already open
8a: moving lorry?
8b: lorry
4c: uniform


4411: read doors in new screen.
	de = 0xa7c0[2*a]
	hl = c3d0
	++ix[0]
	c=*de
	*hl++ = *de++
	*hl++ = c450[c-1]
	*hl++ = b046[c-1]	; door type.
	*hl++ = *de++
	if de[-1] == 6:
		hl[-2] = de[-1]
	*hl++ = 0
	*hl++ = *de++
	*hl++ = *de++
	; do something with a720[2*(a-1)]

find door drawing...
771c: read c3d1
7722: read c3d3
7725: read c3d5
7728: read c3d6



5011: draw door character: hl = src; de = dst; bc = size; a = high y bits and operation (h,0,l,a[6:7]; d,0,e,a[4:5]; b,0,c,0; 0,0,0x90|a[0:3]

77d8: draw N door
77f3: draw S? door
7738: draw door with jump map @773c