Add Fairy to Platinum

* For US Platinum (3541). Needs to be a fresh ROM that's still 128MB or you can't re-insert the expanded file.

* Use crystaltile2 for this tutorial.

Insert the Type Chart
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* Export overlay9_0021.bin from the ROM.
(Open the file viewer by clicking the DS icon in the toolbar. Scroll down to overlay9_0021.bin, right click it and hit export.)

* Open the file in a hex editor. Paste the hex string below at the end of the file (so it's appended to the end).
(The hex string contains the type chart as of Gen 6, including Fairy matchups for ??? and the modified Ghost/Dark vs Steel matchups).

00000A00010A00020A00030A00040A00050500060A00080500090A000A0A000B0A000C0A000D0A000E0A000F0A00100A00110A
01001401010A01020501030501040A010514010605010814010905010A0A010B0A010C0A010D0A010E05010F1401100A011114
02000A02011402020A02030A02040A02050502061402070A02080502090A020A0A020B0A020C14020D05020E0A020F0A02100A02110A
03000A03010A03020A03030503040503050503060A030705030800030914030A0A030B0A030C14030D0A030E0A030F0A03100A03110A
04000A04010A04020004031404040A04051404060504070A04081404090A040A14040B0A040C05040D14040E0A040F0A04100A04110A
05000A05010505021405030A05040505050A05061405070A05080505090A050A14050B0A050C0A050D0A050E0A050F1405100A05110A
06000A06010506020506030506040A06050A06060A060705060805060905060A05060B0A060C14060D0A060E14060F0A06100A061114
07000007010A07020A07030A07040A07050A07060A07071407080A07090A070A0A070B0A070C0A070D0A070E14070F0A07100507110A
08000A08010A08020A08030A08040A08051408060A08070A080805080914080A05080B05080C0A080D05080E0A080F1408100A08110A
09000A09011409020A09030509040A09050A09060A09070A09080509090A090A05090B0A090C0A090D0A090E0A090F0A091014091114
0A000A0A010A0A020A0A030A0A040A0A05050A06140A070A0A08140A090A0A0A050A0B050A0C140A0D0A0A0E0A0A0F140A10050A110A
0B000A0B010A0B020A0B030A0B04140B05140B060A0B070A0B080A0B090A0B0A140B0B050B0C050B0D0A0B0E0A0B0F0A0B10050B110A
0C000A0C010A0C02050C03050C04140C05140C06050C070A0C08050C090A0C0A050C0B140C0C050C0D0A0C0E0A0C0F0A0C10050C110A
0D000A0D010A0D02140D030A0D04000D050A0D060A0D070A0D080A0D090A0D0A0A0D0B140D0C050D0D050D0E0A0D0F0A0D10050D110A
0E000A0E01140E020A0E03140E040A0E050A0E060A0E070A0E08050E090A0E0A0A0E0B0A0E0C0A0E0D0A0E0E050E0F0A0E100A0E1100
0F000A0F010A0F02140F030A0F04140F050A0F060A0F070A0F08050F090A0F0A050F0B050F0C140F0D0A0F0E0A0F0F050F10140F110A
10000A10010A10020A10030A10040A10050A10060A10070A100805100900100A0A100B0A100C0A100D0A100E0A100F0A10101410110A
11000A11010511020A11030A11040A11050A11060A11071411080A110905110A0A110B0A110C0A110D0A110E14110F0A11100A111105
FEFE00000700010700FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

* Save the file, then go back to crystaltile2, right click overlay9_0021.bin, and hit import. Select the file you just edited.

* crystaltile2 will say the file is too small and to enter a new location. Just hit OK and it'll do it. (This won't work if the ROM has been trimmed!) The ROM should have autosaved (despite crystaltile2 telling you otherwise if you try to close the ROM).

Repoint to the New Type Chart
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* Extract overlay9_0016.bin and open it in a hex editor.

Search for "D4 EC 26 02". There should be four instances. Replace all four of these with "80 9F 1E 02".
Search for "D5 EC 26 02". There should be three instances. Replace all three of these with "81 9F 1E 02".
Search for "D6 EC 26 02". There should be three instsances. Replace all three of these with "82 9F 1E 02".

* Save and import overlay_16 back into the ROM. The file size is the same so this should just work.

The game is now using your new type chart. You'll need to change moves/Pokemon to the ??? type to take advantage of the Fairy matchups. Or adjust that type chart as needed for a different type (Snow).

Once you've done this, you should be able to set the ROM in PPRE to separate it into files, then replace with your already edited files and it should all work.