Digging basins to the lower rim left a 9-18 grain vertical cliff on each lake's high side (owner screenshots, seed 766733). From each edge inward the ground now falls at most 0.7 grains a column and is never raised above the natural surface. New no-cliff check in t_lakes.js; world hashes re-baselined (shallow ore: 2 cells changed, on a lake bank). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>