Alien Syndrome (Arcade)

Alien Syndrome is a top-down fast-paced action game where players must rescue hostages while shooting at aliens.

Unused Music#

The game has a handful of tracks that go unused. Some of the tracks were later used in the X68000 port.

Object Display#

This screen is accessible in service mode after the memory test finishes. Normally a branch instruction prevents it from running, but the following patch NOPs it out so it is accessible again:

Set: aliensyn
maincpu.mw@1C60E=4E71
maincpu.mw@1C610=4E71

The object display screen allows you to cycle through sprites (PAT NO), palettes (COL NO), orientation (DIR NO), and adjust the palette color data.

Controls#

Sprites of interest#

There are some Sega characters that make an appearance in the object list.

Character Display#

This screen is accessible in service mode after the memory test finishes. The game sets up a pointer to the code that runs this editor but overwrites it with the game's reset entry point during the memory test. The following patch redirects the branch that skips the object display screen to instead go to the character display screen.

Set: aliensyn
maincpu.mw@1C610=08A8

On this screen character data is grouped into 64 tiles and four groups are displayed for 256 tiles total.

• Up/Down selects the group's palette to edit
• Left/right selects the digit to edit of a palette
• Button 1/2 adjusts the selected digit
• 1P/2P start advances the grouping by 256 characters

Leftover Source Code#

Fragment of memory test source code at 0x1DCBE:

Return from memory test
* ------ << memory_test >> ------
memotest:
        btst.b  #_TESTSW,SWITCH0
        beq.

Fragment of listing at 0x2BA56:

00961 
00962 *Angle Get to Player (Enemy Bomb) **************************
00963 *     
00964     

References#