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Things Found Under Lifted or Destroyed Objects
1		Things Found Under Lifted or Destroyed Objects
2		(Bushes, Grass squares, Rocks, Rock Piles, Pots, Signs, and Big Square Blocks)
3		Mini Algorithm Guide
4		Version 1.0
5		by Assassin
6		21 August 2013 (and some mysterious earlier date, if the Deja Vu is believed)
7
8		_______________________________________________________________________________
9
10		Upon lifting, slicing down, or bombing a bush (which can be green, purple, or
11		brownish green), lifting a rock (which can be small or large, light or dark,
12		normal or skull), lifting a pot (which can be brown or a skull), lifting a sign
13		(which can be brown or yellow), slicing or bombing a square of grass, dashing
14		into a rock pile, or lifting a large, gray, square block, the game performs the
15		following steps to determine what will be found under it:
16
17		1) If there is a nonzero item ID assigned to the lifted/destroyed object, skip
18		to Step 5.
19
20		2) If we're indoors, skip to Step 5.
21
22		3) If what we're looking under isn't grass or a normal green (not brownish
23		green) or purple bush, skip to Step 5.
24
25		4) This step will "randomly" choose an item ID for what's under a bush or
26		square of grass, as there was no specific entity assigned to it (or Item ID
27		00h - Nothing was literally assigned to it). It has several substeps:
28
29		A. Randomly skip to Step 5 one half of the time.
30		B. If there are four or more non-Link sprites/monsters onscreen (not
31		counting Sprite 6Ch, whatever that is), skip to Step 5 to avoid
32		overcrowding.
33		C. If we're not in at least Phase 2 of the game (i.e. we haven't brought
34		Princess Zelda to the Sanctuary yet), then skip to Step 5.
35		D. Get our current square of the map. It'll be a 0-63 value, as the
36		overworld maps are 8x8 grids. Two notes:
37		- Large map sections are 2x2, with one square number taking the place of
38		4 positions. For example, the Mysterious Woods / Skeleton Forest is
39		all indexed with Position 0, rather than with 0, 1, 8, and 9.
40		- The square number actually comes from the bottom 6 bits of a Screen
41		Number variable, which holds 0 - 63 for normal Light World map screens,
42		64 - 127 for normal Dark World map screens, and 128+ for special
43		screens (e.g. the Master Sword screen, the camp under the bridge, and
44		Zora's Lake). The top two bits are ignored. So the Zora area, for
45		instance, is screen 129, but gets treated like it's Screen 1 (whose
46		random prize/sprite data is a duplicate of Screen 0 - Mysterious
47		Woods, and doesn't disable anything). This oversight allows for a
48		crazy, garbled looking foe to turn up, as Zora's Waterfall lacks the
49		tile set to properly display the Green Soldier.
50		E. Load our 0 to 7 bush/grass prize pack counter, which indexes two prize
51		packs (one for each world) of eight entries each. Increment it for our
52		next use (wrapping to zero if it exceeds seven). On the GBA version,
53		it apparently loads the post-incremented value instead.
54		(Note that this counter is reinitialized to 0 after a system reset or
55		powerdown, even if you'd saved your game. However, on the SNES version,
56		it is retained after Saving, Quitting, and reloading (and you can even
57		temporarily copy it between save slots by saving on one, then loading
58		another).)
59		F. The prize packs for each world are:
60
61		Light World = 01h, 01h, 01h, 01h, 0Fh, 01h, 01h, 12h
62		(Green Rupee, Green Rupee, Green Rupee, Green Rupee, Green Soldier
63		with Sword, Green Rupee, Green Rupee, Ground Bomb / Land Mine)
64		Dark World = 10h, 01h, 01h, 01h, 11h, 01h, 01h, 03h
65		(Awakening Skull Rock, Green Rupee, Green Rupee, Green Rupee,
66		Blue Helmeted Bull with Poker, Green Rupee, Green Rupee, Bee)
67
68		Get the Item ID from the slot indexed by our loaded prize pack counter.
69		However, instead proceed to Step 5 without loading an Item ID if both of
70		these conditions are met:
71		- Our intended prize pack slot is preventable in the current world (see
72		list); that is, it has a nonzero prevention flag.
73		- The current map square has this prevention flag present in its list of
74		exclusions. (Each square has a single list used for both worlds.)
75
76		Preventable "random" sprites:
77		Light World = Slot 4, Slot 7
78		(Green Soldier with Sword, Ground Bomb / Land Mine)
79		Dark World = Slot 0, Slot 4
80		(Stal / Awakening Skull Rock, Blue Helmeted Bull with Poker)
81
82		5) If we're indoors, skip to Step 7.
83
84		6) Randomly exit and return nothing one half of the time.
85
86		7) If an ID of 00h (or nothing) was originally assigned to the bush/grass/rock/
87		pot/rock pile/sign/block, and Step 4 did not change it by picking a new ID,
88		exit and return nothing.
89
90		8) If an ID of 04h (Random) was originally assigned to the lifted/destroyed
91		object, randomly pick an item ID ranging from 13h through 16h. Otherwise,
92		just stick with the assigned ID.
93
94		9) Convert the Item ID into a sprite using the table below. If the sprite is
95		00h (Nothing), then don't actually put that on the map (as it'd be a
96		Crow/Raven or Kyune/Horned bird), but exit and don't return anything.
97
98		Item ID \| Sprite (ID)
99		-------------+------------------------------------------------------
100		01h \| Green Rupee (D9h)
101		02h \| Rock Spider/Beetle/Crab/Hoarder (3Eh)
102		03h \| Bee (79h)
103		04h \| Random (special case - see Step 8)
104		\| (Note that Green Rupee is in the data here, but
105		\| it's just a placeholder.)
106		05h \| Bomb x 1 (DCh)
107		06h \| Heart (D8h)
108		07h \| Blue Rupee (DAh)
109		08h \| Key (E4h)
110		09h \| Arrow x 5 (E1h)
111		0Ah \| Bomb x 1 (DCh)
112		0Bh \| Heart (D8h)
113		0Ch \| Partial Magic refill (DFh)
114		0Dh \| Full Magic refill (E0h)
115		0Eh \| Cucco/Chicken [LW] or Cucco/Chicken skeleton [DW]
116		\| (both 0Bh)
117		0Fh \| Green Soldier with Sword (42h)
118		10h \| Stal / Awakening Skull Rock (D3h)
119		11h \| Blue Soldier with Sword [LW] or Blue Helmeted Bull
120		\| with Poker [DW] (both 41h)
121		12h \| Ground Bomb aka Land Mine (D4h)
122		13h \| Green Rupee (D9h)
123		14h \| Faerie/Fairy (E3h)
124		15h \| Heart (D8h)
125		16h \| Nothing (00h - special case, see above)
126
127		_______________________________________________________________________________
128
129		RECOMMENDED READING
130		_______________________________________________________________________________
131
132		This document doesn't get into which prize pack slots are disabled by which
133		map squares. To see that information, you'll want to consult the "Commented
134		code and data for item uncovering" on my website:
135
136		http://home.comcast.net/~assassin17/zelda3_guides.htm OR
137		http://www14.brinkster.com/assassin17/zelda3_guides.htm
138
139		Compare the map data in the 1A/FB7B structure to the 1A/FBCB or 1A/FBD3
140		structure (depending on which world), and see when common bits are set.
141
142		_______________________________________________________________________________
143
144		CREDITS
145		_______________________________________________________________________________
146
147		- Susan Carriere, for suggesting I create a more readable document to
148		supplement the commented disassembly of the findings under bushes, grass,
149		rocks, etc. Then for providing various helpful feedback on the document:
150		suggesting a preamble, pointing out a step omission which would have allowed
151		keys under pots being randomly missable, asking for elaboration on
152		preventable random prizes, clearing up ambiguity in Step 8, and suggesting I
153		account for the different-sized rocks (which eventually led to me listing
154		every relevant covering object).
155
156		- Lady_Birdo for pointing out that the glitched enemy at Zora's Waterfall was
157		a soldier. I couldn't tell what I was looking at.
158
159		- BaronDante for explaining that the glitched appearance stems from the
160		soldier's tile set not being loaded in that area.
161
162		_______________________________________________________________________________
163
164		REVISION HISTORY
165		_______________________________________________________________________________
166
167		Version 1.0: 2009 and maybe 2010; July 10-13 and 15, 2013; August 14-16, 18-19,
168		and 21, 2013:
169
170		- Released a commented disassembly on July 12, 2009, after starting work on
171		it sometime before March 27, 2009. But that wasn't necessarily readable by
172		most humans.
173		- Starting in August 2009 and maybe extending into early 2010, wrote a
174		document that had about 90% of the step content you see here. However, I
175		never uploaded it anywhere, as it wasn't quite done, and the hard drive of
176		the computer housing it crashed. :O I couldn't stomach the idea of
177		re-composing something I'd already done, and figured I'd retrieve it
178		whenever the hard drive was restored. (It's probably just a service sector
179		issue.) However, by mid 2013, still having yet to bring the disk anywhere,
180		I had an epiphany that I am even cheaper than I am lazy. So I decided to
181		bite the bullet and remake the document.
182		- July 10-13 and 15, 2013: Wrote document, then improved it based on Susan
183		Carriere's suggestions.
184		- August 14-16 and 18-19: Added "Stal" as a name for the skull rock enemy, and
185		"Hoarder" and "Crab" for the Rock Beetle/Spider. Added Credits and Revision
186		History sections. Added GBA and reset/reload info to Step 4E.
187		- August 21, 2013: Released document.