Obstacle

An obstacle is a type of square that blocks players, orbs, or both from passing through it. There are three main types of obstacles, along with a class of special obstacles that exist only on the mind altar. Note that these obstacles are classified by function; for example, the lava in the fire altar is classified as water even though it is not, literally, water.

Barrier
The barrier (not to be confused with barrier (defence)) blocks both players and orbs from passing through it, and is also the only type of obstacle that blocks line of sight. It is colored black in the emulator.

Rock
The rock blocks both players and orbs from passing through it, but does not block line of sight. It is colored grey in the emulator. Defensive barriers are considered rocks.

Water
The water blocks players but not orbs, and does not block line of sight. It is colored various colors in the emulator (brown in the air altar, blue in the water altar, and yellow in fire altar).

Panel
The panel is a one-dimensional obstacle which acts like a thin barrier. Panels are implemented as floor squares, as objects can walk on them, which are blocked with a thin barrier in a particular direction. Panel squares can be divided into three classes: These three panel types suffice to create any desired geometry of panels in a map.
 * West panel: A floor square with a thin barrier on its west side.
 * South panel: A floor square with a thin barrier on its south side.
 * Southwest panel: A floor square with a thin barrier on both its west and south sides.

Minipillar
The minipillar is a zero-dimensional obstacle which blocks players and orbs, but only if they are moving diagonally across it, and only in one of the two diagonal orientations. There are two types of minipillars: To remember which minipillar is which, it is helpful to recall the idea of the main diagonal in linear algebra, which is the diagonal of a square matrix that runs from top left to the bottom right; for example, the trace of a matrix is the sum of the entries along its main diagonal. Similarly, the "main" minipillar, that is, minipillar 1, is the minipillar which blocks the top-left to bottom-right direction of travel.
 * Minipillar 1: Blocks players and orbs from passing from northwest to southeast.
 * Minipillar 2: Blocks players and orbs from passing from northeast to southwest.