Sonic the Hedgehog 2 (8-bit) AutoDemo

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Sonic the Hedgehog 2 AutoDemo
System(s): Sega Game Gear
Publisher: Sega
Developer: Aspect Co. Ltd
Genre: Action

The Sonic the Hedgehog 2 AutoDemo is a Sega Game Gear EPROM cartridge demonstrating the then-upcoming release of Sonic the Hedgehog 2. It was sent to several magazines worldwide for preview purposes. On July 14, 2014, Orengefox obtained a copy of the AutoDemo, and the ROM was released to the public in August.

As the name may suggest, this Sonic 2 AutoDemo is not playable - instead, the demo plays itself, starting with a simplified introduction sequence and title screen (much like the final game), before continuing with Sonic running through an early version of Green Hills Zone (complete with loop), gliding through a largely empty Sky High Zone, and briefly riding one of Underground Zone's mine carts. Following this, a static "Coming Soon" screen appears, and the demo loops from the beginning.

A single music track plays throughout the demo - one not present in the final game. Much is different from the retail release of Sonic 2, most notably the introduction and title screens and the Green Hills Zone tileset. Tails is also completely missing.

Many early screenshots of the game shown during development are thought to originate from this demo - the primary giveaway being that as gameplay is always the same, the ring and time counts at specific points never change. Furthermore as the HUD resets at the start of each of the three sections, Sonic is seen using a hang glider mere seconds into play - in the final game there are no opportunities to use one this early.

The AutoDemo has an internal date code of 1991-12-05, nine months before the final's date of 1992-09-05.

Differences

• The SEGA screen is different and plays no "SEGAAA" chant.
• The title screen only features Sonic, who has no animation (but rises from behind the ribbon)
• The title screen has no sound.
• The minecart wheel sits above the rail, rather than inside
• The lightning flashes in sky high zone are different, and are in the priority plane (i.e. in front of the Sonic sprite)
• The art of Green Hills zone is completely different, being more similar to the credits sequence of the final version
• Sky High didn't have trees or flowers in this prototype and seems to be an earlier version than the one featured on the magazines
• Underground zone has many tiles that didn't make the cut, including gray bricks and curvy stone pathways
• There only appears to be art for 3 levels. Green Hills zone, Sky High zone and Underground zone.
• The sound of jumping on a spring is the same as the "rolling down a hill" sound.

Gallery

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  Following a standard Game Gear "Sega" screen, a brief, Sonic-only intro before the title screen.

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  Sonic is dropped into a very different Green Hills Zone and begins running to the right, occasionally jumping, collecting rings and using a ramp.

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  He runs around a heavily scripted loop, before exiting mid-stage.

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  Sonic then handglides through a very empty Sky High Zone for a while.

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  Then he falls and lands on an Underground Zone mine cart, which rolls down a hill.

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  Finally, a "coming soon" screen appears and the sequence repeats.

Hacking

Following release, the ROM was quickly disassembled with control restored to the player. Traversing the stages further reveals a number of hidden and non-functioning objects, such as springs (of which only the vertical types function), spikes and breakable walls, as well as more of the prototype tileset and artwork.

Green Hills Zone is much longer than what is usually shown and almost resembles a completed stage. Underground Zone utilises several tiles unused in the final game, including what is thought to be a tube (similar to those found in Sonic 1's Green Hill Zone) and some sort of building. Sky High Zone also has platforms.

Given the very early state of the code, there are many bugs affecting Sonic's movements. Loops do not function correctly when entered at the "wrong" speed, less control is afforded to the player while on springs and Sonic can roll simply by ducking and pressing right or left (i.e. there is no initial momentum requirement). It is impossible to die - Sonic can fall off-screen but is almost always able to jump back on, and exiting the playfield on the right pushes Sonic several pixels to the left in an unclean fashion.

Many sound effects are incorrect or nonexistent, and the music track never changes. Hills do not affect Sonic's speed in any way, making some areas with rings impossible to reach, and the ring and time counters in the HUD have no effect on the game when they max out.

External Links

• 
  Sonic Retro discussion thread
• Video of the AutoDemo