Created Smashing rocks has a chance to contain items (markdown)

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+In HGSS, XY and ORAS, it is possible to use Rock Smash and instead of encountering a Pokemon (or nothing...), you could also find an item from a small table of potential item drops.
+
+This tutorial will go over how to achieve that functionality in pokecrystal. (This feature was adapted from [Polished Crystal](https://github.com/Rangi42/polishedcrystal), huge thanks to Rangi!)
+
+
+
+## Contents
+1. [Modify the overworld functionality](#1-modify-the-overworld-functionality)
+2. [Adding the rock item code](#2-adding-the-rock-item-code)
+
+
+## 1. Modify the overworld functionality
+
+First, we must edit the `RockSmashScript` within [engine/events/overworld.asm](../blob/master/engine/events/overworld.asm):
+
+```diff
+	callasm RockMonEncounter
+	readmem wTempWildMonSpecies
+-	iffalse .done
++	iffalse .no_battle
+	randomwildmon
+	startbattle
+	reloadmapafterbattle
+-.done
+	end
+
++.no_battle
++	callasm RockItemEncounter
++	iffalse .no_item
++	opentext
++	verbosegiveitem ITEM_FROM_MEM
++	closetext
++.no_item
++	end	
+```
+
+These changes stop the `RockSmashScript` from ending if it doesn't find a Pokemon, jumping to `.no_battle` if the game does not startle a Pokemon hiding within the rock, and then calling `RockItemEncounter` to determine whether or not an item will be rolled. If no item is rolled, the script will jump to `.no_item`, ending the script and giving the player nothing. 
+
+But `RockItemEncounter` has yet to be defined, so these changes on their own will not work.
+
+
+## 2. Adding the rock item code
+We have to define `RockItemEncounter`, and a suitable place to put it would be in [engine/events/checkforhiddenitems.asm](../blob/master/engine/events/checkforhiddenitems.asm) at the bottom of the script:
+
+```diff
+.GetFarByte:
+	ld a, [wBuffer1]
+	call GetFarByte
+	inc hl
+	ret
++
++RockItemEncounter:
++	ld hl, .RockItems
++	call Random
++.loop
++	sub [hl]
++	jr c, .ok
++rept 2
++	inc hl
++endr
++	jr .loop
++.ok
++	ld a, [hli]
++	cp $ff
++	ld a, NO_ITEM
++	jr z, .done
++	ld a, [hli]
++.done
++	ld [wScriptVar], a
++	ret
++	
++.RockItems:
++	db 1, MAX_REVIVE
++	db 2, THICK_CLUB
++	db 4, NUGGET
++	db 6, STAR_PIECE
++	db 12, BIG_PEARL
++	db 18, ETHER
++	db 24, HARD_STONE
++	db 24, SOFT_SAND
++	db 48, PEARL
++	db 64, BRICK_PIECE
++	db 48, NO_ITEM
++	db -1
++
+```
+
+For starters, `RockItemEncounter` will load the  `.RockItems` table into `hl`, and then call `Random`. `Random` is what the game uses to generate a lot of random statistics and variables, a good example would be the stats and specific Pokemon of a wild encounter.
+
+It rolls a chance to obtain an item, and if true, then `Random` will pick an item from the `.RockItems` table. The numerical values next to each item on the table is the percentage chance the player will receive said item, in this scenario a `MAX_REVIVE` has a chance of 1%.
+
+If `Random` rolls and lands on `NO_ITEM`(48%), then no item will be given, and the script will jump to `.done`, and back to executing the rest of the `RockSmashScript`.
+
+If `Random` rolls and lands on any item in the table, it loads it into memory and heads back to the `.no_battle` part of `RockSmashScript`, giving the player whatever item `Random` found.
+
+
+
+And there you have it, the player can now find items within smashed rocks! You can add your own items and chances by editing the `.RockItems` table in `checkhiddenitems.asm`, or even add something more complex like the Fossils/Old Amber from RBY.
+
+![Screenshot](https://i.imgur.com/E1CW3yK.png)
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