d4 Crystal Shard Die

Modern crystal-shard d4: a slim square crystal prism 0.024 m long and 0.010 m across flats, each end drawn to a four-facet point like a quartz crystal, dead-flat faces and 0.6 mm chamfers.

风格：low-poly, flat-shaded vertex colors, no textures, 2 materials: the shared opaque one plus a distinct surface (glass, water or chrome), which stays its own mesh through mergeAssets rather than merging into the rest; shares palette and scale with its kit