- Tubes run in eight directions: a drag at about 45° lays a diagonal run, R cycles all eight. - Diagonal runs carry grains at the straight rate (120 grains/s), join straight tubes and belts, keep grains in at the corners, pass water, and carry bars level. - New part ids 11-14 (saved ids are never renumbered); tube checks use an IS_TUBE table. - New test/t_diag_tubes.js (85 checks). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>