Multiple Tank Glitch
The Multiple Tank Glitch is a glitch in Microsoft's version of Chip's Challenge caused by adding a tank to the monster list multiple times. It does not exist in other rulesets, and it is one of only a handful of glitches that is not emulated by Tile World.
For other monsters that are added to the monster list multiple times, the square simply spawns more the number of monsters equal to the number of instances in the monster list. This is not true of tanks, which only spawn once no matter how many times it is added to the monster list - except in a few special circumstances. These special cases can achieve very bizarre effects in a level designed with this glitch.
If the tank has a sliding tile buried underneath it, then a curious effect will be observed if the tank slides on its first move. After the tank leaves the sliding tile, the tile buried underneath the tank will follow the tank and possibly morph itself into a different tile in the process. The exact tile that it morphs into is determined by an algorithm in Chip's Challenge, which is described in more detail in a later section.
For example, consider the starting configuration below, where the tank appears twice in the monster list:
After two ticks, the resulting configuration will be:
Notice how the first force floor appears to have slid two spaces to the right. Suppose instead that the tile under the tank was a west force floor instead of an east force floor. Then the ending configuration would be:
The reason the west force floor now turns into a red lock will be made clearer in the next section.
Tile morphing algorithm
What happens in the above examples is that the force floor actually behaves exactly like a monster for one turn.
Recall that there are four copies of each monster in the tile set, one for each direction. This is important to distinguish the direction in which a monster such as a glider is moving. In order to determine which index tile to choose, Chip's Challenge groups all the monster tiles into sets of 4 consecutive tiles. Within each group, the order of tiles in the set is north, west, south, east. In addition, the first tile in each group has an index that is a multiple of 4.
In this glitch, tiles that are not normally monsters are also grouped as such since they behave as monsters for one turn. In the first example, the tiles Clone block S, Clone block E, Force floor N, Force floor E are grouped together as one monster unit - although in reality, this grouping does not make any sense since these are not monsters. Note that Force floor E is designated as the "east" tile in this group, since it is the last tile in the group. This is why the east force floor happens to remain unchanged while it slides east.
In the second example, the west force floor is the first tile in the group Force floor W, Exit, Blue lock, Red lock. As the red lock is the tile that is designated "east" in this group, this is what the west force floor turns into as it slides east. By extension, one can expect that if the second example were flipped so that the west force floor now slides west, it will turn into an exit (which is the "west" tile of its group), and this is indeed what happens.
Possible tile morphs
This diagram shows many possible tiles that can be created using the glitch. Each group of 4 tiles is outlined in a unique color, where the topmost tile in the section would be the "north" tile, followed by "west", "south", and "east". Using this diagram, one can predict that if the tank starts on a SW ice corner and moves south, the ice corner will turn into a fake blue wall. If it instead moved east, it would become a real blue wall, and if it moved north, the ice corner would remain the same tile.
There are also other tiles that can be created which cannot be achieved through simply morphing a tile one time (these tiles have dotted outlines). If a real blue wall created using the glitch is bumped into while it is sliding, it will morph into a water tile, as this is the designated "east" tile of the group the regular wall is in - Floor, Wall, Computer chip, Water. If a block is pushed into the water tile as it is sliding, it will become dirt and can then morph into a south or east thin wall. It can also morph into another block if it slides to the south, though once it does the tile will not be able to morph again.
Furthermore, if Chip has flippers, he can step on a sliding water tile without being killed, at which point it will morph into a Swimming Chip tile, leaving Chip on a floor in the space it previously occupied. Monsters and Chip can also be turned into sliding tiles by having the monster or Chip step onto a sliding tile they can occupy such as a floor; although this will also not allow for further tile morphing. Interestingly, this leaves behind a copy of the monster on a floor tile while the original monster continues down its path, after which the monster that was sliding will begin to move around normally. If a Chip or Swimming Chip tile created with the glitch is killed, the game will act as if the real Chip has been killed, similar to the effect if multiple Chip tiles are placed in a level.