Oracle RNG algorithm

; Note: b, c, h, and l are all 8-bit values which can be combined into 16-bit values.

; RNGlo is address 0xFF94; RNGhi is address 0xFF95.

; On hard reset, RNGlo is set to 0x37. RNGhi is set to 0x0d.

; Load hl and bc with current RNG values
ld a,(RNGlo)
ld l,a
ld c,a
ld a,(RNGhi)
ld h,a
ld b,a

; multiply RNG by 3
add hl,hl
add hl,bc

; Store the new value into RNGhi.
ld a,h
ld (RNGhi),a

; Add the new hi and lo bytes together, and store it in RNGlo.
add a,c
ld (RNGlo),a

; Return the new value of RNGlo in register A.
ret