Crystal Lattice Unit Cells (2D)

This top-down companion renders the same four unit cells as the 3D crystal lattice scene — simple cubic, body-centered cubic, face-centered cubic and hexagonal close-packed — viewed flat from above instead of orbited in 3D. Projection mode flattens a full cell's atoms onto the page with depth shown only as a brightness cue, while cross-section mode sweeps a horizontal cutting plane through the stacked spheres and draws the exact circle each one leaves behind at that height. Atoms per cell, coordination number, nearest-neighbour distance and packing fraction are all recomputed live from the current structure and atomic radius rather than looked up from a table, so scrubbing the radius slider away from the touching radius visibly opens gaps between spheres or forces them to overlap.