Orthot is a 3D puzzle in the "Excessive Internal Complexity" genre.
Each puzzle is a separate challenge, the goal of which is to reach the marked exit point (Represented as a trasparent blue object with an "E" inside). Puzzles are built out of a collection of puzzle elements which you may interact with and which interact with each other. There are a wide variety of types of puzzles which you may encounter: Mazes, hidden object search, arrangement of blocks into particular patterns, logical problems, evasion of hostiles, or whatever else can be built out of interative blocks.
It is the successor of Orthot II, which in turn was the successor of Orthot I.
Orthot III is also an Open Source Project and is hosted on github: https://github.com/Eketek/orthot