NES Dr.Mario RNG simulator

rand.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

RAND_INI = 0x8988

def BIT(x, i):
    return (x>>i) & 1

def rand_update(r):
    bit = BIT(r,1) ^ BIT(r,9)
    r >>= 1
    r  |= bit << 15
    return r

def main():
    r = RAND_INI
    s = set()
    s.add(r)

    while True:
        print(f"0x{r:04X}")
        r = rand_update(r)
        if r in s: break
        s.add(r)

    #print(len(s))

if __name__ == "__main__": main()