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Metroid Improved RNG

Hack of Metroid


This replaces the original (extremely bad) Metroid USA random number generator with an enhanced random number generator to fix the many issues random number generation in the original causes. Otherwise, gameplay is identical to the original cartridge version.

Version 1.1 fixes some bugs in and further optimizes the random number generation routine and removes some of the code from the original game that did not need to be patched. It also includes source code with some instructions on how to use it.

Known issues:

  • Polyps do not work properly if the game is loaded after a fresh boot in Norfair. If you leave and reenter Norfair, or start the game in another area and then travel to Norfair, they should work fine. This is actually present in the original NES game as well and fixing it is in scope but I am still working on that.
  • The random number generator state is destroyed when transitioning between areas or exiting.
  • Serious memory corruption occurs during the Mother Brain boss fight.

These latter two issues will be fixed in an upcoming patch.

ROM / ISO Information:

  • Database match: Metroid (USA)
  • Database: No-Intro: Nintendo Entertainment System (v. 20180803-121122)
  • File SHA-1: ECF39EC5A33E6A6F832F03E8FFC61C5D53F4F90B
  • File CRC32: A2C89CB9
  • ROM SHA-1: FDBFC7871962F72A1EF57E5A7E456164FB93430B
  • ROM CRC32: 70080810




ContributorType of contributionListed credit
tertuHackingASM work

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