Afterburner Easter Egg (Dev Credits)

Today I decompiled a portion of Afterburner II's code to investigate some unused developer text I found in the ROM.

I traced the usage of these strings back through the code, with some manual IDA work. In the end I landed on the following function which enables the related block of code:

This revealed that the text could be triggered on the Continue Play screen, providing the player hadn't already inserted a coin.  On this screen you must press the cannon button (fire 1) four times, the missile button (fire 2) twice, followed by the cannon button again. 

On inserting a coin and resuming the game, a (c) SEGA 1987 message will now be shown:

Message 1: (c) SEGA 1987

But what of the other text strings? Unfortunately, it appears that you can only display them using the Mame debugger. The routine to display them is present in the code, but the counter to select the message (which should increment each time you do the cheat), is broken as it resets when the Continue Play screen initializes. I think the original intention was to cycle the message each time the player entered the cheat code, but for whatever reason that never happened. 

You can manually set the counter (0x3F9126) to override this behaviour. Let's take a look: 

Message 2: Presented By Sega

Message 3: I Love Momoko

Message 4: Programmer Credits

What's interesting is Satoshi Mifune's name appears in the credits here, who later programmed titles including Shenmue and Virtual Striker. It's very difficult to find out the dev team members of these early AM2 titles, so great to have this proven. I wonder who Momoko was... 

I also investigated Afterburner I. It contains a similar routine, but is tougher to activate. This is because after pressing fire1 x4 and fire2 x2, you must almost simultaneously coin-up and start.