Under the microscope: Shellshock (PlayStation)

Hidden “greets” to the Amiga demoscene in a 1996 PlayStation game

Let’s talk about Shellshock, the 1996 game from Core Design – the studio that made the first Tomb Raider games.

If you look at most cheat sites, you’ll find a few codes listed:

Screenshot from GameFAQs

Of these, only Cheat Menu actually works. IGN and many other sites repeat the bogus ones.

The hidden Cheat Menu

Correct instructions for the Invincibility code can be found on the Wayback Machine. Developer Derek Leigh-Gilchrist posted them to his personal website shortly after the game was released:

Cheat #2 (infinite armour)

• Load up your SHELLSHOCK and start a game as normal, then when you are playing level #1 select QUIT GAME from the options menu to return to the titlepage...

• Now QUICKLY press the following buttons on your joypad:-

• Up,Up,Up,Down,Down,Down,Right,Right and then TRIANGLE..

• You will hear a noise confirming that you have infinite armour!

*NOTE* this cheat will NOT work the FIRST time the titlescreen appears, so remember to play a game first...

How do these codes work? I found the function that checks for the button sequence in the game data. Here’s Ghidra’s decompilation of it with labels added (all memory addresses are for the PAL version):

void check_cheat_8003fd48(int *cheat_buttons_1_)
{
  int *cheat_buttons_2_;
  
  if ((p1_held_800889b8 != p1_held_80088a7c) &&
     (p1_held_80088a7c = p1_held_800889b8, p1_held_800889b8 != 0)) {
    cheat_buttons_2_ = cheat_buttons_1_ + cheat_counter_80088a8c;
    cheat_counter_80088a8c = cheat_counter_80088a8c + 1;
    if (p1_held_800889b8 != *cheat_buttons_2_) {
      cheat_counter_80088a8c = 0;
    }
    if (cheat_counter_80088a8c == 9) {
      cheat_effect_80087560 = 1;
      cheat_counter_80088a8c = 0;
      play_sfx_8003dc38(0x2a,0x7fff,0x1e00,0);
    }
  }
  return;
}

This is a typical bit of “cheat sequence detection” code. Each time you press a button from the sequence, a counter increments. If you make a mistake, the counter resets. Once you’ve completed the sequence, an effect is applied and a sound effect plays.

Ghidra finds three references to this function. One is for the Cheat Menu code. Another is for the Infinite Armor code. And the third seems to be new!

The sequence lives at 80084d88, and looks like this:

0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x10

It gets read when you’re on the Credits screen, which is accessible via the Cheat Menu.

The Credits screen

0x80 corresponds to the Left button and 0x10 corresponds to the Triangle button. So the full instructions for entering this code are:

• At the title screen, enter Up, Down, Left, Right, Down, Down, Right, Right, Square.

• At the cheat menu, select Credits.

• On the Credits screen, enter Left (x8), Triangle.

If you got it right, an Easter egg from the aforementioned Derek Leigh-Gilchrist will appear:

The Easter egg screen

The text says:

greets to Chs,Jon,Spex,
all the core lot
all the codies lot (yo!)
tom@cydel.com (package?)
all on #amigascne (supernao!)
email me (the coder)
del@nlights.demon.co.uk

The “codies lot” refers to Codemasters, where Derek Leigh-Gilchrist worked prior to joining Core Design. Who Chs, Jon, Spex, and Tom are remains a mystery, however – if you have an idea, leave a comment.

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Outro

Alas, this Easter egg isn’t in the Saturn version of Shellshock. As far as I can tell, it only has one cheat code – a different cheat menu. Check out Sega Retro for instructions on how to use it.

For more on credits Easter eggs, see the articles on E.T. Interplanetary Mission, The Crow: City of Angels, and Batman: Vengeance.