4D Polytopes is an educational and reference app that allows users to visualize and manipulate four-dimensional objects. Developed by Sci-Tech Binary Ltd. Co., this iPhone app offers a real-time rendering of convex regular polytopes in four dimensions, such as the tesseract, as well as three-dimensional Platonic solids. With simple touch gestures, users can intuitively rotate and interact with these geometric figures.

The app provides various touch gestures for different functionalities. One-finger gestures allow users to rotate the displayed polytope in three-dimensional space, while tapping stops the rotation. Two-finger gestures enable rotation between the hidden fourth spatial axis and the other axes, specifically for the four-dimensional polytopes. Three-finger gestures allow users to switch between different polytopes of the same dimensions, as well as between four-dimensional and three-dimensional views.

In addition to touch gestures, the app offers several effect options. Users can toggle between colorful and white light to illuminate the polytopes, and they can choose to sync the light sources with the rotation of the polytopes. The app also allows users to mark specific cells or faces of each polytope in their selected color. Furthermore, there is a Wikipedia button that provides links to articles describing the polytopes, with an English button available for non-English articles. Users can capture still and moving images on the screen with the provided buttons, and they can adjust the angle of the color light sources and the marking color.

For those interested in stereopsis, the app includes a switch that enables cross-eyed or parallel viewing of the polytopes, allowing users to merge two images for a three-dimensional effect. Overall, 4D Polytopes offers a unique and interactive way to explore the world of four-dimensional geometry.