The Multiple Tank Glitch, also known as Multi Tank Bug, is a special case of the Multiple Monster Glitch in which a tank is added to the monster list multiple times.
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.
Note: a sliding tile is defined to be any of the five ice tiles or any of the four directional force floor tiles.
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 likes 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 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.
Levels that use the glitch
- Evan Dummit: inanity.dat - (most of the levels in the set)
- ChipHome5: ChipHomeIS.dat - (most of the levels in the set)
- Tyler Sontag: TCCLPRejects.dat - Four for the Price of One