================================================================================

                    THE LITTLE MERMAID - CO-OP EDITION

                  A two-player co-op hack for the NES game
                           "The Little Mermaid"

                               Version 1.0

================================================================================

This is a game I owned and played when I was a kid. I always wanted to make an NES co-op hack, 
and I chose this game as it has, in my opinion, some of the better graphics on the NES.

--------------------------------------------------------------------------------
 PATCH INFORMATION
--------------------------------------------------------------------------------

  Hack name .......... The Little Mermaid - Co-op Edition
  Version ............ 1.0
  Released ........... 2026-07-28
  Author ............. robowalter
  Platform ........... Nintendo Entertainment System (NES)
  Hack type .......... Improvement / Game-play modification

--------------------------------------------------------------------------------
 DESCRIPTION
--------------------------------------------------------------------------------

  The Little Mermaid on the NES is a single-player game. This mod adds a
  fully playable second Ariel, so the whole game can be played co-operatively
  by two people on one console.

  The hack also includes a CPU HELPER mode, in which the second Ariel is
  controlled by computer. She follows the human player around, chases enemies
  that appear on screen and shoots at them.

  A difficulty setting has been added. NORMAL plays as the original;
  HARD makes enemies much faster and gives bosses more lives.

  Both options are chosen from menus on the title screen. Everything else -
  levels, items, music, graphics and the story - is untouched save for occasional bug.


--------------------------------------------------------------------------------
 WHAT IS NEW
--------------------------------------------------------------------------------

  * Two-player simultaneous cooperative multiplayer
      A second Ariel is controlled from controller port 2. Both players swim, attack,
      carry shells and open chests independently.

  * CPU HELPER mode
      In this mode the second Ariel is controlled by computer. She follows the human
	  and attacks any enemies she sees. She tries to go around obstacles. She gets damage
	  but her lives are infinite and she doesn't cost player any lives.

  * NORMAL / HARD difficulty
      Hard makes every enemy move three times as fast and doubles
      lives for every boss. 

  * Title screen menus
      Two small menus were added to the title screen for the above.
	  To make room for it original hidden developer menu was removed.

  * Increased number of starting hearts from 3 to 5
	  Since both players share same health bar it was necessary to increase number of starting hearts.


--------------------------------------------------------------------------------
 HOW TO START A GAME
--------------------------------------------------------------------------------

  Press START on the title screen. Two menus appear in turn:

    1.  COOP  /  CPU HELPER
    2.  NORMAL  /  HARD

  In each menu, press LEFT or RIGHT to move the arrow and START to confirm.
  After the second menu the game begins as normal.


--------------------------------------------------------------------------------
 CONTROLS
--------------------------------------------------------------------------------

  Player 1 - controller 1, and Player 2 - controller 2, both use the game's
  original control scheme:

    D-PAD ............ swim
    A ................ attack / throw a carried object
    B ................ swim faster
    START ............ pause

  In CPU HELPER mode controller 2 is ignored, the second Ariel is controlled
  entirely by computer.


--------------------------------------------------------------------------------
 NOTES AND KNOWN LIMITATIONS
--------------------------------------------------------------------------------

  * Hearts and lives are shared between the two players, exactly as the
    original game's single life bar works. There is no separate meter for
    the second Ariel, although number of starting hearts was increased from 3 to 5.

  * If first Ariel swims far ahead, the second Ariel is left behind and cannot be seen.
    While she is off screen she is protected from harm and can swim back into view
	under her own power. If she is left off screen for around three seconds she is
    moved in view automatically.

  * In CPU HELPER mode the computer-controlled Ariel does not lose hearts
    when she is hit. This is deliberate - she is meant to assist the player,
    not consume the shared life bar through mistakes the player did not make.

  * HARD is designed to be challenging, but can be beaten with enough effort.

  * The original game already has a noticeable lag in some areas as it's a heavy game for NES,
    the second player increases it slightly, if this seems problematic you
	can use overclocking options such as those found in MESEN emulator.
	For Mesen specifically I found that under Options -> Emulation -> Overclocking these settings
	make the game run smoother:
		Additional scanlines before NMI: 2
		Additional scanlines after NMI: 2
		Clock Rate Multiplier: 200%
		Do not overclock APU: enabled
	If I ever get around to releasing an update I might look into optimizing this.
	
  * In the first Ursula boss battle second mermaid will be drawn incompletely,
    this is a known bug and might be fixed in future releases if I find time for that.
	
  * The hack has been tested in Mesen, FCEUX and Smolnes. Other accurate
    emulators and flash carts should work, since no mapper behaviour or
    timing was changed.


--------------------------------------------------------------------------------
 VERSION HISTORY
--------------------------------------------------------------------------------

  1.0  -  2026-07-28  -  First public release.


--------------------------------------------------------------------------------
 CREDITS
--------------------------------------------------------------------------------

  Hack, programming and testing
    robowalter

  Original game
    The Little Mermaid (NES) - developed and published by Capcom, 1991.
    All original code, graphics, music and characters remain the property
    of their respective owners.

--------------------------------------------------------------------------------
 DISTRIBUTION AND LEGAL
--------------------------------------------------------------------------------

  This is a free, unofficial fan modification. It is not affiliated with,
  endorsed by, or connected to Capcom, Nintendo, or The Walt Disney Company
  in any way.

  Only the patch file is distributed. No copyrighted ROM data is included,
  and none may be distributed with it. You must supply your own copy of the
  original game.

  This patch may be freely redistributed provided that it is distributed
  free of charge, that this readme accompanies it unaltered, and that credit
  is retained.

================================================================================
