Mechanics and controls

Origin HeartGold changes more than the story. These notes describe v4.0.3, checked against the original Chinese game’s code. The EXP/EV award example and information-screen controls were also checked in the emulator. Where a full gameplay test is still missing, the limits are stated below.

Information-screen controls

These are Nintendo DS buttons, not particular keyboard keys. Use the corresponding buttons in your emulator or on your controller.

Where	Button	Action
Pokémon summary, stats/moves page	L	Show IVs and EVs together
IV/EV panel	L or B	Close the panel
Battle command menu	Y, or tap the information button at the top right of the touch screen	Open battle information
Battle-information panel	B	Close the panel

If the first Y press only highlights a battle command, press Y again. The panel shows information such as stat stages and your Pokémon’s ability; it is not a promise that an opponent’s unrevealed ability will be visible.

The summary shortcut was tested with normal button settings. R did not open the IV/EV panel in that mode, despite the game’s L/R hint.

Automatic EXP and EV sharing

Your party shares battle experience points (EXP) and effort values (EVs) automatically. EVs are training points that affect a Pokémon’s stats; IVs are its individual stat values.

In a controlled battle, the participating Pokémon received 26 EXP, the benched Pokémon 13 EXP, and both gained 1 HP EV. This illustrates the nonparticipant half-EXP path, not a promise that every battle gives those amounts. Eggs, fainted party members and every special battle mode were not tested.

There is no native on/off setting for this sharing in the inspected v4.0.3 battle code. You do not need the held Exp. Share to enable it. Keep party-wide EV gains in mind when training.

Capture chains

The Chain Logger is added to your Bag during new-game setup. Use it to inspect your chain and the area’s encounters.

Catching the same species and form builds a chain. The bonuses use the number already caught before the next encounter is generated:

Completed catches	Hidden Ability selection chance from the chain	Distinct IVs forced to 31
0–5	No chain bonus	0
6–9	10%	1
10–19	50%	2
20+	70%	4

A Pokémon may naturally have more perfect IVs. Hidden Ability selection still depends on that species’ ability data.

The game’s displayed ranges are inaccurate around 10 and 20. The verified boundaries are 6, 10 and 20 catches. Shiny chances also improve, but the displayed fractions do not establish the exact combined probability; they should not be used as precise odds.

• Catching a different species or form starts a new chain at 1.
• Catching a shiny of the same species and form clears the chain.
• A shiny of a different species or form follows the new-chain rule and starts at 1.
• Defeating or fleeing does not advance the chain; no reset on those actions was found in the inspected handlers.

The bonuses can apply to a different species from the one you chained, including the traced scripted wild encounters. Gifts, Eggs and every special encounter are not covered by that verification. The chain counter stops increasing at 255.

EV Allocator

The EV Allocator is added after battle if you do not already have one. This is verified in the battle-end code; the exact first acquisition screen has not been replayed.

It redistributes EVs you already earned. It does not create new training points. Before exiting, you must restore each party member’s total to the amount it had when you opened the tool.

Button	Action
Left / Right	Decrease / increase the selected EV by 4
L / R	Decrease / increase it by 64
X / Y	Previous / next party member
SELECT	Open the clear-EVs confirmation
START	Open the restore-entry-EVs confirmation

These allocator mappings were read from the normal-button-mode handler; all confirmation and alternative-button-mode combinations have not been played through.

Mom’s charms

Mom’s savings purchases include these three charms. Each purchase is queued for delivery and deducts money from your savings; reaching a threshold does not mean immediate receipt.

Charm	Savings threshold	Cost from savings
Catching Charm	$30,000	$3,000
Exp. Charm	$40,000	$3,000
Shiny Charm	$50,000	$3,000

The inspected reward paths do not include an Oval Charm. That does not establish whether it can be obtained elsewhere.

Visible encounters and shinies

The game supports up to six visible wild Pokémon nearby. Repel suppresses new visible spawns; immediate removal of existing spawns was not verified. Ordinary encounter frequency is reduced in some conditions while visible Pokémon are present, but it is not an unconditional one-third rate everywhere.

A visible shiny has a sparkle and sound cue. The game keeps one temporary shiny record and can use it when you re-enter the same map, searching for a position near you. Terrain can still prevent an accessible placement, and another shiny can replace the single record.

Catch a visible shiny before restarting. The retained record is cleared during game boot. Do not rely on an ordinary save to preserve it: save/load restoration has not been established. Emulator save states are a separate mechanism.

Special calendar encounters modify particular land encounters on annual dates. They are listed separately from the ordinary location tables.

Evolution

The hack rewrites many evolutions. Each Pokémon page lists how it evolves, read from the game code, and what changed from HeartGold. The main rules:

• No trading needed for the old trade evolutions. Kadabra, Machoke, Graveler, Haunter and the rest now evolve when they level up holding an item, often only by day or by night (for example Haunter → Gengar holding a Spell Tag at night, Machoke → Machamp holding a Black Belt by day). Onix and Porygon simply level up.
• Day and night: night is 20:00–3:59, “day” is 4:00–19:59. A few evolutions need 10:00–16:59 and say so.
• Friendship: “high friendship” means 220 or more; Sylveon needs 158 or more plus a Fairy-type move.
• The first match wins: Meowth, Slowpoke and Cubone must take their held-item evolution before the level of their normal one, and Eevee checks Sylveon and Espeon before Glaceon.
• Some evolutions can’t happen: a few methods in the data are never checked by the game (Pancham → Pangoro, Gimmighoul, Kubfu and others; Moss Rock Leafeon and magnetic-field Probopass, which still evolve with a Leaf Stone or Thunder Stone). See Known issues.

Held-item forms

• Charizard holding Charizardite becomes Mega Charizard X. Any nature except Timid or Modest.
• Charizard holding Charizardite becomes Mega Charizard Y. Timid or Modest nature.
• Mewtwo holding Steel Armor becomes Armored Mewtwo. No nature requirement.
• Greninja holding Ninja Scroll becomes Ash-Greninja. No nature requirement.

These are held-item transformations, not permanent evolutions. Removing the required item returns the Pokémon to its base form. The transformation rules are verified in the game code; every animation and item-change sequence has not been replayed.

Other training and battle changes

• Pickup: successful Pickup deposits go straight into the Bag. An empty held-item slot is not required by the inspected routine. Full-Bag behavior was not tested.
• Held items after battle: the game restores many items, but has exceptions, including special berry handling. Do not assume every consumed, stolen or knocked-off item comes back.
• Hatching: both Flame Body and Magma Armor enable an eight-cycle decrement. Small remaining counters decrease more slowly, so this is not exactly eight times fewer steps for every Egg. Multiple holders do not stack in this routine.
• Destiny Knot: either parent holding it raises inherited IV slots to five. This does not guarantee five perfect IVs.
• Everstone: a single holder supports nature inheritance, but the two-holder and different-language breeding paths prevent a blanket guarantee. Those exceptions have not been tested with a full Egg-hatching series.

Field moves

The hack intentionally lets you use scripted obstacle moves without teaching them to a Pokémon. Badge requirements still apply, and party-menu moves have separate restrictions. See the field-move table for the precise distinctions.