LADX Blob Manip Full Report

THE BLOB MANIP:
    In action: https://cdn.discordapp.com/attachments/104346010041458688/581991381330034688/2019-05-26_01-32-38.mp4

    This only works if a bomb trigger is used to start the fight and there is no music.

    There are four sword slash sounds. Slash the sword until one of sounds 2 or 3 occur,
    then hold the sword. The quick kill will work, assuming positioning is correct.

    Sound 0: https://cdn.discordapp.com/attachments/104346010041458688/582625747521503235/sword_00.wav
    Sound 1: https://cdn.discordapp.com/attachments/104346010041458688/582625766601392163/sword_01.wav
    Sound 2: https://cdn.discordapp.com/attachments/104346010041458688/582625773811400715/sword_02.wav
    Sound 3: https://cdn.discordapp.com/attachments/104346010041458688/582625778739707935/sword_03.wav


HOW IT WORKS:
    RNG depends on the frame counter [ffe7], the LY register [ff40], and the previous RNG
    value. LY (the current scanline being rendered) is fairly consistent when there's no
    music, so we need not worry about it. (Although it's possible that slight variance in
    LY could cause occasional failures.)

    The blob always checks RNG when [frameCounter]%4 == 3 (maybe mod 8?). Bits 0 and 1 of
    the frame counter will affect the blob's decision. But since those bits are
    consistent, we only need to "prepare" the RNG value accordingly.

    The sound the sword makes depends directly on what the current stored RNG value is.
    There are four distinct sounds, which tell you what the current value modulo 4 is. The
    lowest bit will be discarded since there's a "shift right" operation, but we can still
    influence bit 1, the second lowest bit. This is why sword sounds 0/1 and 2/3 act the
    same.


BROADER APPLICABILITY:
    What this manip does is it affects the lowest bit of the RNG, meaning it can be used
    to force 50/50 decisions one way or another. But the circumstances are very specific.

    LY becomes extremely variable when music is playing, making it unlikely that similar
    manips could be done in other situations.

    The blob's frame rule, where he always checks RNG while the frame counter has
    a particular value, is also important. This might not be uncommon, though. Many
    animations in link's awakening depend on the frame counter, rather than an internal
    timer. Try freezing the frame counter [ffe7] to see how messed up everything gets.


ROM addresses:

00:2812: "Get RNG value" function
15:525e: Blob decides whether to disappear


RAM addresses:

1:d368: Write here to play music
1:d369: Write 00 here to stop music

ffe7: Frame counter
fff3: Write here to play a sound effect