It is unlocked simultaneously when Trail 2 is unlocked, which was introduced in Update 1.7. There is a special option available in the Trails section to ‘Enable glow’, which forms an outline of the selected secondary colour to surround the edges of the selected icons.
The trailer for Ultimate Destruction uses the cube unlocked for completing 'Can't Let Go' in normal mode.The eighth trail in the old version of Geometry Dash World.
