Under the microscope: Kaitou Saint Tail (Saturn)

Who ya gonna call?

In this edition, we’re going to look at an Easter egg in Kaitou Saint Tail, the 1997 Saturn game. It’s based on the Saint Tail manga / anime series, and was published in Japan by Tomy.

After starting a new game, you eventually get control of Meimi, a.k.a. Saint Tail. The game’s clock starts at 08:00 AM.

08:00 in Saint Tail’s house

You’re meant to leave the house and get to school by 09:00, but if you’re late, the game will take you directly there (and you’ll be scolded for your tardiness). Once you’re in the classroom, it’s time to pick a minigame.

The minigame selection screen

The minigame that you play isn’t predetermined. When you press A or C on the selection screen, a virtual wheel starts spinning. You can press A or C to stop it, and whatever game comes up is the one you play.

The function at 06012518 implements the minigame selection screen’s logic. It works like this:

• The wheel’s position is updated every 8 frames.

• The position cycles through 16 values (0 through 15).

• When you stop the wheel, its position is rounded down to the nearest even number.

• That even number is used as an index into a list of minigame files.

Here’s how it looks with the a reduced frame rate:

The list of minigame files has eight entries. You’ll play the one whose index comes up on the wheel. They’re vaguely school-themed, and range from P.E. to cooking.

But wait: there’s some extra logic that executes before the wheel starts spinning. It looks like this in pseudo-Python:

while True:
    if ((held_button & 0x0400) != 0) and ((held_button & 0x0200) != 0):
        update_frame_0600b21c()
        timer_06041ece += 1
        if timer_06041ece == 30:
            timer_06041ece = 0
    else:
        break

if ((held_button & 0x0080) == 0) and ((held_button & 0x0008) == 0):
    # ...
    load_file_0600ebd0("\\mini\\mini9.bin")

That is, the game waits for you to press A or C (hex patterns 0x0400 and 0x0200). Once you do, it checks to see whether you’re pressing both R and L (hex patterns 0x0080 and 0x0008). If you are, it loads a hidden 9th minigame.

In this game, your opponent sends ghosts at you. You’re meant to stop them with a fireball attack. If three of them make it past you, you lose. But if you last long enough, you win.

Left: Game over. Right: Saint Tail wins!

Here’s a video of the game in action:

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Outro

Thanks for reading! For another breakdown of an Easter egg like this, see my article on the Puffy boss fight in NiGHTS Into Dreams.

I’ll be back with more retro game reverse engineering articles soon - many thanks for reading.