Sfera - sliding puzzle in curved space

3D space may have some curvature. Sfera helps you realize that.
It's a sliding tile puzzle game (like the classic 15 puzzle), but its space is curved.
The board has no bounds — it's closed in on itself.

Click to slide a tile.
Drag to rotate.
Use the mouse wheel to evert the space.

Each puzzle level starts in a solved state. Just explore at first: spin it, mess around, reset.

Then choose a mission — it shuffles the tiles. Try to restore the initial state manually.
The next level unlocks when you complete 2 out of 3 missions.

GPU required: Shader Model 3.0 (with Vertex Texture support), e.g. DirectX 9.0c.
Windows and Android versions include sound.

Implementation details for geeks

The game space has constant positive curvature — it’s a stereographic projection of a 4D sphere.
Each level is built on a 2D surface (currently a sphere or a torus) embedded in this space. The surface is divided into tetragonal cells to hold the tiles. These cells are further subdivided into smaller parts to define coordinates for sliding tiles smoothly.
Tile vertex geometry is computed in the Vertex Shader. The coordinates of the subdivided cells are passed to the shader using Vertex Texture.

The core shader functionality is available on GitHub.