Controls

Geometry

The "A" key toggles the boundary texture from shape color to white. See Settings for the whole story.

Control-R reloads the current scene from the scene file. This is very handy if you're working on some changes to the file.

Trains

The keys X-C-V are the train speed control. "V" speeds the train up, "X" slows it down, and "C" brings it to a full halt immediately. "X" can also take it into reverse.

The "Q" key toggles the track from multi-rail to monorail. In 3D it's just a matter of taste, but in 4D the setting you want depends on what you're doing. The multi-rail track can be slow to draw, especially in large scenes, but it's interesting to look at up close, especially at junctions and helices.

Switching

The space bar is used to control switching. To use it, first point at the tile you want to control. In 3D that's easy enough, but in 4D it can be a bit of a challenge. You'll either need to move around until you're directly above the tile you want to control or switch to non-aligned mode and use the turn keys as a three-dimensional mouse. Either way, it's a good exercise in 4D thinking!

The track starts off all orange. As you switch it, one segment at a time will become red, then when you've gone full circle it will all be orange again. When there's a red segment, trains will choose that segment to move on if they can, otherwise they'll choose at random.

I don't know of any situation where this is useful, but the pointing code doesn't check for obstacles, it just projects your line of sight down to the ground plane and switches that tile.