Glass

Glass is the first obstacle of the game. It can broken by balls. Glass may hook on to a metal (e.g. belts and cylinders) or may move. It is usually seen in every checkpoint in random appearances.
 * In Checkpoint 7, Glass Cannons throw cubes of glass to the player.
 * In Zen Mode, they will mostly appear as a pane in normal exhibitions, and cubes in Zero Gravity (and stage 2) exhibitions.
 * Pre-Alpha builds use opaque glass.