Jack% FAQ

Q - What are you trying to accomplish?
A - This is a mini romhack of Pokemon Red called PC Jack.  My goal is to beat the game as fast as possible without using glitches.

Q - What is changed in this romhack?
A - Only one byte of the game's code was changed, allowing the player to get an item called Cancel from the PC instead of the Potion.

Q - What does the Cancel item do?
A - Cancel is a glitch item that has an effect that allows the player to walk through solid walls of up to 2 tiles, providing the player is facing away from the wall.  There are several glitch items with this effect.  The first one discovered was called Jack, so this item is more commonly referred to as Jack instead.

Q - How does this item allow you to walk through walls?
A - Jack has the effect of opening your Pokemon menu (and it actually heals HP when used), but it is not programmed as an item that opens your Pokemon menu.  When the Pokemon menu is opened normally, the game saves the position and direction of all sprites on the screen so that it can replace them with the sprites of the Pokemon currently in the party.  When you close the Pokemon menu afterwards, the game still thinks you're facing the direction you were facing before using the item, allowing you to walk sideways or backwards.  The game only checks the tile in front of the player to see if movement can be made in a direction, and since the player is facing a different direction than he is moving, you can walk through obstacles until the tile in front of the player is solid.  This allows to clip through 1-tile walls, or 2-tile walls if the player is facing opposite the wall.  In addition, we can bypass trainers in several areas because the game doesn't load them until they come onscreen, and their sprites will never come onscreen.