Neural Tube Closure: Hinge-Point Folding Simulator (2D)

This 2D companion to the 3D neural-tube model strips neurulation down to a single cross-section: a chain of 24 neuroepithelial cells whose apical (inner) edges narrow relative to their fixed basal (outer) edges wherever apical constriction is applied, with each cell's own width ratio converted directly into the wedge angle it contributes to the fold. Dial down median or dorsolateral hinge-point constriction, or the folate/methylation factor both hinges depend on, and watch the same real geometry that closes the tube in vivo either seal the cross-section shut or leave the two fold edges standing open — a live, cell-by-cell demonstration of why neural tube defects are a mechanical failure of hinge-point folding, not just an abstract risk factor.