Diagonal tubes as thick as straight ones, with centred elbows where they join (t35)

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

docs/PROJECT_MAP.md

@@ -356,10 +356,10 @@ Drawing (src/render/): browser only. This file: the renderer state R, colour tab
 Propagated coloured light from glowing and burning cells.
 - functions: builtForLight, looseForLight, computeLight
 
-### src/render/world.js (361 lines)
+### src/render/world.js (410 lines)
 Scale colour without changing the smooth-look class.
-- functions: fogColor, diagonalTubeBlock, drawWorld
-- variables: TUBE_CLASS
+- functions: fogColor, diagonalTubeJoins, diagonalTubeShape, diagonalTubeBlock, drawWorld
+- variables: TUBE_CLASS, diagonalJoins, diagonalAcross, diagonalAlong, diagonalCap
 
 ### src/render/machines.js (242 lines)
 Machine overlays: fans, engines, silo and the rest, drawn on top of the world.
@@ -374,7 +374,7 @@ Smooth look: WebGL setup, texture uploads, drawing and adaptive resolution.
 - functions: smCompile, smoothAvailable, smUpload, smoothDraw, smoothPace
 - variables: SM, smBytes
 
-### src/render/smooth-shaders.js (348 lines)
+### src/render/smooth-shaders.js (366 lines)
 Smooth shaders: vertex and fragment programs for the rounded world look.
 - variables: SM_VS, SM_FS
 
@@ -467,7 +467,7 @@ Gamepad input.
 - functions: padPressed, pollPad
 - variables: PAD
 
-### src/ui/previews.js (199 lines)
+### src/ui/previews.js (216 lines)
 Cursor previews: shared grid helpers, air streaks and tool preview dispatch.
 - functions: blockRectPx, drawGrid, previewColor, drawAirStreaks, drawReachCircle, drawPreviews, previewBlock
 
@@ -476,7 +476,7 @@ Drill previews: shaken rock cracks, pulse wavefronts and aiming fan. Rock the dr
 - functions: crackSeg, drawCracks, pulseRGB, fanPoints, drawDrillPulses, drawDrillAim
 - variables: CRACK_N, CRACK_LV
 
-### src/ui/preview-selection.js (80 lines)
+### src/ui/preview-selection.js (81 lines)
 Selection previews: labelled tags, copy and cut boxes, and paste ghosts. a small labelled tag drawn on the world (screen pixels)
 - functions: drawTag, drawSelection, drawPastePreview
 - variables: SEL_COL
@@ -547,4 +547,5 @@ The frame loop and boot.
 - `tools/scenes/stone-uses.js`: The stone and sand machines: a half-full silo with its gate open over a belt, a stone cutter fed with rubble, and cut stone and glass brick walls. Run clear-sky.js first, e.g. python3 tools/shot.py /tmp/stone.png --setup tools/scenes/clear-sky.js --js "$(cat tools/scenes/stone-uses.js)" --ticks 240 --zoom 7
 - `tools/scenes/t33-ground.js`: Paused dug pocket: copper ore, rubble and dirt against stone, granite and dirt. Use --js "..." to set daylight or R.lens after this setup; CAM frames the pocket.
 - `tools/scenes/t35-diagonal.js`: Run after clear-sky.js: a belt takes sand from a pile, up a diagonal screw to an upper belt.
+- `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.