Sandcastle Stability: Wet-Sand Cohesion & Critical Wall Height (2D)

This 2D companion replaces the 3D version's decorative build-up animation with the actual granular mechanics behind why a sandcastle wall stands up at all: a capillary-bridge cohesion model driven by moisture content and grain size, fed into Culmann's Mohr–Coulomb critical-height formula alongside the wall's own batter angle and the sand's friction angle, so the tower you watch being poured genuinely stalls, tapers or slumps to its angle of repose based on real soil-mechanics thresholds rather than a fixed timer.