Corner placements of screw conveyors stay separate ends (t62 follow-up)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/DESIGN.md

@@ -486,6 +486,11 @@ above, including:
   on warns first that the save will be marked, and the mark stays with the world; any future
   achievements won't unlock in a marked world. Besides money, items and upgrades it may have
   game speed and other things just for fun.
+- **Screw conveyors only join a diagonal on the same row (t62, 2026-10-27).** A straight screw
+  joins a diagonal when it sits right beside the diagonal's end block, and that join is drawn
+  as an elbow. When the diagonal instead starts one block lower or higher, so the two only touch
+  corner to corner, they stay two separate ends and nothing passes between them. The owner tried
+  a corner join and found it looked odd, and building it that way is unusual anyway.
 
 ## Ideas not built yet
 

docs/PROJECT_MAP.md

@@ -265,9 +265,9 @@ Pipes, pumps and outlets: each joined line holds one liquid as a count, not as g
 Per-tick machine work: steam engines, fans, belts, filters, screw conveyors (machinesTick).
 - functions: engineIntake, fanBlow, machinesTick
 
-### src/sim/conveyors.js (208 lines)
+### src/sim/conveyors.js (198 lines)
 How belts, filters and screw conveyors move what is on or in them. What rests on a belt or filter rides along: the whole stack standing on the carrying surface steps one cell toward d together (belts run front of the line first, so the way ahead is clear). If a powder grain is blocked, the load above it stands still and the belt slips underneath. A filter's own material drops through it instead, unless it is already full.
-- functions: conveyorStep, carryColumn, beltDrain, launchGrain, rebuildFilters, filterCarry, carryBeltsAndFilters, setFilter, filterRun, roomFor, screwSpread, screwIntake, straightScrewNext, diagonalScrewNext
+- functions: conveyorStep, carryColumn, beltDrain, launchGrain, rebuildFilters, filterCarry, carryBeltsAndFilters, setFilter, filterRun, roomFor, screwSpread, screwIntake, diagonalScrewNext
 - variables: CARRY_DEPTH, filterR, filterL, filtersDirty
 
 ### src/sim/slope-conveyors.js (230 lines)
@@ -284,7 +284,7 @@ Molds: cavities for castings; ingot troughs empty themselves below. Removal retu
 - functions: moldCellsAt, canPlaceMold, newMoldRecord, addMold, castMix, cavityState, troughState, clearCavity, moldPlugCells, rakeAbove, furnaceJunkHint, unplugMold, ejectIngot, checkMolds, moldAt, tally, collectMold, removeMold
 - variables: DROSS, grains, barWord
 
-### src/sim/items.js (295 lines)
+### src/sim/items.js (288 lines)
 Bars and other loose objects (ents), and the bag: adding, taking, costs and refunds.
 - functions: entSolidCell, entSupportCount, entFreeAt, entMark, spawnBar, removeEnt, entScrewAt, entScrewFree, entScrewMove, entScrewLane, entScrewEdge, entScrewEnter, entScrewTick, entDiagonalScrewTick, entSlopeBeltTick, entTick, entsInCircle, bagAdd, bagTake, giveOrDrop, refundAt, canAfford, payCost, fmtMoney, costText, needText
 - variables: BAR_W, BAR_H, entCurM, droppedLast
@@ -367,7 +367,7 @@ Drawing only: the face stays on its simulation cells; the band hangs below it.
 - functions: slopeBeltConnections, flatBeltCaps, prepareSlopeBelts, slopeBeltSegment, slopeBeltCorner, slopeBeltShape, slopeBeltAt, slopeBeltColor, screenLoaded, slopeWallShape, slopeWallAt, slopeDetailAt, slopePreviewCleat
 - variables: slopeBeltJoins, slopeBeltHalo, beltCaps, slopeAcross, slopeAlong, slopeDistance, slopeWallOwner
 
-### src/render/diagonal-screws.js (74 lines)
+### src/render/diagonal-screws.js (68 lines)
 Screw casing geometry shared by both looks, ghosts and placement previews. smooth-look class of a screw conveyor cell by direction: 9 up, 10 right, 11 down, 12 left
 - functions: diagonalScrewJoins, diagonalScrewShape, diagonalScrewBlock
 - variables: SCREW_CLASS, diagonalJoins, diagonalAcross, diagonalAlong, diagonalCap
@@ -393,7 +393,7 @@ Smooth look: WebGL setup, texture uploads, drawing and adaptive resolution.
 Smooth slope shading, kept beside the shared CPU geometry in slope-belts.js.
 - variables: SM_SLOPE_HELPERS, SM_SLOPE_DRAW
 
-### src/render/smooth-shaders.js (373 lines)
+### src/render/smooth-shaders.js (370 lines)
 Smooth shaders: vertex and fragment programs for the rounded world look.
 - variables: SM_VS, SM_FS
 
@@ -577,4 +577,4 @@ The frame loop and boot.
 - `tools/scenes/t35-joins.js`: Run after clear-sky.js. Paused, empty pipes make casing, flights and mouths easy to inspect.
 - `tools/scenes/t36-funnel.js`: A twelve-block funnel, one block open at the bottom, draining 400 grains of sand.
 - `tools/scenes/t40-sloped-belt.js`: Self-contained: a flat feed climbs, crosses the top, and runs downhill; a filter sorts below.
-- `tools/scenes/t62-joins.js`: Self-contained grid. Rows: UR, DR, DL, UL. Each run has both end joins. Columns: horizontal edge, horizontal corner, vertical edge, vertical corner; repeat those four with the straight travel reversed. Camera fits --zoom 6 --viewport 2100x1300. Run after clear-sky.js or by itself. Empty, paused screws expose the whole casing.
+- `tools/scenes/t62-joins.js`: Self-contained grid. Rows: UR, DR, DL, UL. Each run shows both ends. Columns: horizontal edge, horizontal corner, vertical edge, vertical corner. Corner columns stay unconnected, with two separate ends. Repeat those four with the straight travel reversed. Camera fits --zoom 6 --viewport 2100x1300. Run after clear-sky.js or by itself. Empty, paused screws expose the whole casing.

docs/agent-log.md

@@ -4,6 +4,19 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-27: t62 corner placements stay separate (Claude Code + Codex)
+
+- Owner tried the corner join and found the jog odd; decision (recorded in DESIGN.md): only
+  same-row joins connect. Removed join kinds 5/6 and `straightScrewNext`; `diagonalScrewNext`
+  and `entDiagonalScrewTick` now continue across a corner only into a diagonal running the same
+  way, so a corner straight piece no longer receives grains or bars. Kept the shared geometry
+  file and the smooth-look elbow seam fix.
+- Files: `src/render/diagonal-screws.js`, `src/render/smooth-shaders.js`, `src/sim/conveyors.js`,
+  `src/sim/items.js`, `src/sim/machine-tick.js`, `test/t_diag_screws.js`, `test/t_smooth.py`,
+  `tools/scenes/t62-joins.js`, `docs/PROJECT_MAP.md`, `docs/DESIGN.md`.
+- Tests: `python3 test/run_all.py --browser` all passed; determinism diff changed only the
+  replaced corner checks.
+
 ## 2026-10-27: t62 screw conveyor joins (Claude Code + Codex)
 
 - Straight screws touching a diagonal's end only at the corner now join, in both looks and in