::===============
::COVID Captives
::By eskayelle
::May 2020
::===============
::
::**CONTENTS**
::
::*****INTRODUCTION*****
::*****VERSION HISTORY*****
::*****TOOLS USED*****
::*****CREDITS*****
::*****ADDITIONAL NOTES*****
::
::
::*****INTRODUCTION*****
::
::With the apartment buildings next door taking most of the hits, 
::yours is the last house on the block (and perhaps in the city) 
::that hasn't been infected with the coronavirus.  
::
::Armed with an experimental vaccine, motor(home) your way through 
::as many strains as you can before COVID takes over your household.
::Fight back against misinformation and pseudo-cures.  
::How many rounds will your stay-at-home strategy last?
::Fight the good fight!
::Stay home!
::Stay safe!
::Play this game!
::
::A graphics hack based on Taito's Space Invaders for the Famicom, 
::COVID Captives grabs those lovable Dr. Mario virus sprites 
::and puts them in an unprecedented situation.
::
::This hack also uses a minor ASM / hex edit to remove the 2nd player option, 
::as the original game failed to properly clear the playfield when swapping 
::between player 1's and player 2's progress.
::
::The COVID Captives vx.x [J] [h].nes file is a modified Famicom Space Invaders ROM.
::The romhack is distributed as an IPS patch, which should be patched to an original Space Invaders ROM. 
::
::The ROM can be opened and played via several emulators, including in Windows, 
::Linux, and Android environments.
::
::
::*****VERSION HISTORY*****
::
::v1.0 (May 2020):
::Modified invaders sprites to reflect Dr. Mario viruses and pills.
::Modified player sprites to display a house.
::Text edits using table editor to reflect COVID-19 theme.
::Adjusted palettes to reflect three color viruses in game.
::ASM hack to remove the 2P function.
::
::
::*****TOOLS USED*****
::
::TileMolester v0.16
::TBLater v1.0
::HxD v1.7.7.0
::FCEUX v2.2.3
::
::
::*****CREDITS*****
::
::eskayelle for all ASM hacking and sprite and tile edits within this hack.
::Taito for the original Famicom game.
::Nintendo for them Dr. Mario sprites.
::John Riggs for his YouTube channel on hacking NES games.
::
::
::*****ADDITIONAL NOTES*****
::
::ASM Hacking--
::A RAM search indicates RAM offset $0055 changes from 00 to 80 when pressing Select.
::Setting a breakpoint on $0055, points to $00:82F5 (command STA $0055 = #$00).
::A search in HxD and a NOP (#$EA) on STA $0055 function eliminates the 2P game. 
::Search for 85 55 4C D1 82 68.
::NOP there; EA EA to 00:82F5 (85 55)
::
::$0201 in RAM appears to impact round numbers and score hundreds place.
::
::$01A0 in ROM is the palette color for the "1 PLAYER" screen; changed to #$0F (black).
::
::At $153B are the sprite palettes when the player is hit.
::
::At $0189 are the sprite palettes for the game.