Sonic the Hedgehog 2 (Nick Arcade Prototype)

The Nick Arcade Prototype of Sonic the Hedgehog 2 is named so due to the similarities to a build that was shown at-least twice on the Nick Arcade Show in 1992. The build is very incomplete, and reuses many assets from the 1st game.

The cartridge was brought by drx thanks to a $1500 community effort, and was dumped onto Hidden Palace and made public on November 7th, 2006.

General Notes

 * Remnants of ToeJam & Earl REV00 can be found at the end of the cartridge. As the developers used burnable EPROM cartridges, it's likely the cartridge used to occupy ToeJam & Earl.
 * While the Summer CES '92 was stated to share the same properties as this build, it was built after May 30th. It's possible that this is actually the Mean Machines Build, as Hill Top Zone seems to be the same one from the '92 issue.
 * The cartridge came with a holographic label, which was a scrapped concept, though it was pretty faded when drx got it.

Differences

 * There's many leftovers from Sonic 1 in this version.
 * 2-Player Mode is very incomplete, the mode functions like 1-Player Mode, though split-screen is implemented. It's also not enabled for every zone.


 * There's a bizarre mechanic where Sonic bumps off a wall if he runs fast enough, this was removed in the next build.
 * The spindash is a work-in-progress, you can only charge it once, and it plays the rolling sound. Funnily, this functionality was restored in Sonic the Hedgehog Genesis, complete with the non-specific sound.

Green Hill Zone

 * This is actually the stage from Sonic 1.
 * The collision is broken as it hasn't been updated for Sonic 2's format.
 * All necessary changes have been made to make Green Hill work with this build, even the chunks were updated for Sonic 2's size.
 * Most of the art is wrong.
 * The original collision format is actually still present and can be hacked back in.
 * All three Acts have different monitors than Sonic 1, showing that the pointers for the monitor types were changed early in development.
 * All Sonic 1-Up monitors are Tails monitors, showing that the Tails monitor in Hidden Palace was supposed to be a Sonic 1-Up as well.
 * Act 3's boss has no camera lock.

Chemical Plant

 * Named Marble on the level select.
 * The background is more pink.
 * The level layout is very different.
 * The loops have diagonal corners, they were changed in Beta 4.
 * Playing this Zone after Green Hill will keep the broken art from GHZ, but with a different palette.
 * Some of Marble Zone's objects are still part of the debug list.
 * Only Act 1 has been worked on, loading Act 2 or 3 will load Act 1 with Green Hill's ring positions.

Hidden Palace

 * Named Spring Yard on the level select.
 * This is the only stage in this build that isn't included in the final game.


 * Act 1 seems to have been worked on while the monitors were still using their Sonic 1 mappings, which explains why there is a Tails 1-Up monitor early in Act 1.

The proper underwater palette, matching the one seen in the Simon Wai prototype, is in the ROM at 0x0027A2. However, the way the game loads the underwater player palette is reused from Sonic 1: If the act number is 03, it loads palette 10 (Labyrinth Zone 4, aka Scrap Brain 3); Otherwise, it loads palette 0F (Labyrinth Zone 1-3). So, the intended underwater player palette is overwritten.
 * The players' underwater palette is the same as in Labyrinth Zone in Sonic 1. This obviously works fine for Sonic, but Tails has some serious problems.
 * If you let the drowning countdown begin then jump out of the water, Labyrinth Zone's music will play.
 * Acts 2 and 3 have not been worked on. Act 2 recycles object placement from GHZ Act 2, while Act 3 uses GHZ Act 3's object placements.
 * Player 2 can control the water level in Act 1 by pressing Up or Down.
 * The boss music plays in Act 3, but there is no boss.
 * Tails acts like he is on land while he is in water. Because of this, his movements are not slowed down, and he cannot drown.

"Labyrinth Zone"
Uses Chemical Plant's tiles, Labyrinth's rippling, and Marble's ring layouts...and it's completely broken.
 * While there are some strips of "land" (garbage data), it is otherwise like Genocide City and Death Egg in the Simon Wai build.
 * If you enter Marble Zone first, then Labyrinth Zone Act 1 will load most of the level.
 * The boss in Act 3 is missing, but the boss music still plays regardless.

Emerald Hill Zone
The most complete Zone in the prototype, and the only one playable without using the Level Select. On Nick Arcade, contestants played Act 1 and had to collect 25 rings in 30 seconds.

This Zone features a badnik that was removed from the final version: a red-shelled snail. This Motobug-like enemy slowly moves around on the ground. When it sees the player, it charges at them (as much as a snail can charge at something, anyway). This enemy was replaced by Coconuts in the final game.
 * The layouts are different.
 * The boss is much less complete, the boss theme plays before the player reaches the boss, and the left boundary is much further than it should be.
 * The boss is in the parked middle, in the final, Eggman descends from the right.
 * The boss theme plays before the player actually gets to the boss.
 * The boundary for the left is way off.
 * Eggman explodes, this isn't the case in the Simon Wai Prototype.
 * The animated cave tiles flash rapidly in the Nick Arcade protoypes. They're at their final animation speed starting in the Simon Wai prototype.
 * This also applies to the tiles in Hill Top Zone.
 * Tails is absent in this zone, as Tails makes you lose rings if he's hit, this was likely done to make the challenge above easier.

Hill Top Zone
In Sonic 1, Scrap Brain Act 3 is actually Labyrinth Act 4. Labyrinth in this build is broken and uses Marble/Chemical Plant's graphics, so this level does as well. The exit to Final Zone is still present, and can be activated by hugging the top of the level and moving to the right via Debug Mode. The palette is a combination of the one from Scrap Brain Zone Act 3 and the cycling colors from Marble/Chemical Plant.
 * Named Scrap Brain & Final on the level select.
 * There's a bunch of leftovers from Sonic 1's Scrap Brain Zone.
 * The screen boundary hasn't been changed from Sonic 1, so following the path will eventually kill the player.
 * In act 2, the game will crash after a certain point, this is because it's trying to load Eggman's PLC, but instead it loads garbage data. Same occurs in Final Zone.
 * While the parallax scrolling has been mostly implemented, the clouds (or whatever they are) in the background don't move on their own yet. The blue mountains far in the back don't scroll yet, either.
 * There have been a few level design changes, but it's similar to the final.
 * Only Act 1 has objects.
 * Lava doesn't harm you as the object that's meant to harm the player hasn't been placed yet.
 * Instead of Sols, the seesaw uses green orbs.
 * The lifts don't drop at the end of their path, and there is only one subtype: The one seen at the start of Act 1. They always move to the right and always stop at the same point.
 * It should be noted that Act 3, if accessed through Act 2 by the ways listed above, will not be empty like Labyrinth Zone, but have a layout consisting of garbage data and Chemical Plant graphics.