Hollow Glass Cubes

Hollow Glass Cubes are an obstacle introduced (prior to Version 1.3.0/Version 1.3.4, it only appeared in 1 checkpoint) in Checkpoint 9. They are just a cube frame, and may hold objects inside them (another cube or an Octahedral Crystal), or just be empty. They also appear in Zen Mode and the Local Multiplayer. They rotate on a cube-shaped metal piece. Sometimes the cubes may spin out of sync.