"Doesn't connect" marks on transport ends that would join one block off (t67 phase 4)

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

docs/PROJECT_MAP.md

@@ -281,10 +281,10 @@ 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/joins.js (73 lines)
+### src/sim/joins.js (125 lines)
 Travel-directed transport ends. Precomputed probes; world/plan queries allocate nothing. End indices stay geometric: left/right, or up/down for vertical screws.
-- functions: pieceEnds, joinCandidate, endJoin, pieceJoins
-- variables: JOIN_ENDS
+- functions: pieceEnds, joinCandidate, endJoin, pieceJoins, endAt, joinIsDrop, joinSnap, nearMiss
+- variables: JOIN_ENDS, NO_PIECE
 
 ### src/sim/conveyors.js (211 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.
@@ -388,7 +388,7 @@ 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/slope-belts.js (169 lines)
+### src/render/slope-belts.js (167 lines)
 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
@@ -398,7 +398,7 @@ Screw casing geometry shared by both looks, ghosts and placement previews. smoot
 - functions: diagonalScrewJoins, straightScrewJoins, diagonalScrewShape, diagonalScrewBlock
 - variables: SCREW_CLASS, diagonalJoins, diagonalAcross, diagonalAlong, diagonalCap
 
-### src/render/world.js (405 lines)
+### src/render/world.js (404 lines)
 Scale colour without changing the smooth-look class.
 - functions: fogColor, drawWorld
 
@@ -406,16 +406,16 @@ Scale colour without changing the smooth-look class.
 Machine overlays: fans, engines, silo and the rest, drawn on top of the world.
 - functions: cellRect, drawHazardRims, drawMachines, drawProcBlocks, drawSilo, drawSiloPixel, drawSiloWindow, drawRackBlocks
 
-### src/render/overlays.js (229 lines)
+### src/render/overlays.js (251 lines)
 Other overlays: floating text, rain and snow, flow arrows, filter tags, molds, the bot, particles.
-- functions: spawnFloater, drawRain, drawFlowArrows, drawRunOutline, drawFilterTags, drawFloaters, moldLabel, drawMolds, drawBot, spawnDebris, spawnSpark, spawnSuck, drawParticles
+- functions: spawnFloater, drawRain, drawFlowArrows, drawJoinMark, drawJoinMarks, drawRunOutline, drawFilterTags, drawFloaters, moldLabel, drawMolds, drawBot, spawnDebris, spawnSpark, spawnSuck, drawParticles
 
 ### src/render/smooth.js (99 lines)
 Smooth look: WebGL setup, texture uploads, drawing and adaptive resolution.
 - functions: smCompile, smoothAvailable, smUpload, smoothDraw, smoothPace
 - variables: SM, smBytes
 
-### src/render/slope-belt-shader.js (126 lines)
+### src/render/slope-belt-shader.js (111 lines)
 Smooth slope shading, kept beside the shared CPU geometry in slope-belts.js.
 - variables: SM_SLOPE_HELPERS, SM_SLOPE_DRAW
 
@@ -480,9 +480,9 @@ The build menu along the bottom: categories, piece tiles and their icons.
 - functions: pieceIcon, catOf, selectBuildCat, cycleBuildCat, buildVariantChips, renderBuildBar, setupBuildBar
 - variables: BUILD_CATS, BUILD_ORDER, PIECE_ICONS, lastBuildKey, lastBuildMenu
 
-### src/ui/selection.js (122 lines)
+### src/ui/selection.js (133 lines)
 Tool selection: cycling, drill tuning, piece variants and costs.
-- functions: pieceSize, pieceUsesWall, setDrillWidth, tuneUnderCursor, cycleItem, cycleWall, rotate, toggleBlow, pickFilterUnderCursor, toggleFilterMat, setBrush, pieceV, pieceExtra, filterBlockAt, chipCost, pieceCostNow, pieceCode, turnSlope
+- functions: pieceSize, pieceUsesWall, setDrillWidth, tuneUnderCursor, cycleItem, cycleWall, rotate, toggleBlow, pickFilterUnderCursor, toggleFilterMat, setBrush, pieceV, dragPlan, pieceExtra, filterBlockAt, chipCost, pieceCostNow, pieceCode, turnSlope
 
 ### src/ui/selection-pickers.js (61 lines)
 Selection pickers: filter rules, filter settings and wall materials. What a filter can hold: loose things and bars you have found, plus anything it already holds
@@ -493,7 +493,7 @@ Selection panels: current tool card and bag materials.
 - functions: renderSelCard, renderBag
 - variables: lastBagKey
 
-### src/ui/info.js (195 lines)
+### src/ui/info.js (200 lines)
 Discovery cards, hover info (I) and the cursor label.
 - functions: showCard, howText, discoveryCard, reactionsOf, hoverInfo, renderInfo, drawCursorLabel, pipeContentsText
 
@@ -506,7 +506,7 @@ Keyboard and mouse listeners.
 - functions: isTyping
 - variables: canvas
 
-### src/ui/actions.js (244 lines)
+### src/ui/actions.js (242 lines)
 What input does: overlays, F, pick, copy / cut / paste, undo, building and tool use each frame. Which overlays are on, shown as a coloured frame round the screen and a named badge
 - functions: updateOverlayUI, toggleLens, doInteract, pickUnderCursor, aimBlock, stampOrigin, selModeHeld, startPaste, stopSelectAndPaste, plural, piecesIn, doUndo, endRmbRecord, dragDirFor, blockLabel, primaryPress, primaryRelease, secondaryPress, toolTick
 - variables: ovShown
@@ -516,7 +516,7 @@ Gamepad input.
 - functions: padPressed, pollPad
 - variables: PAD
 
-### src/ui/previews.js (240 lines)
+### src/ui/previews.js (241 lines)
 Cursor previews: shared grid helpers, air streaks and tool preview dispatch.
 - functions: blockRectPx, drawGrid, previewColor, drawAirStreaks, drawReachCircle, drawPreviews, previewBlock
 
@@ -539,7 +539,7 @@ Shared world colours, minimap and full map.
 - functions: resetMap, mapArea, updateMap, drawMap, mapFit, drawFullMap, openMap, zoomMap, zoomMinimap
 - variables: MAP_S, MAP
 
-### src/ui/loop.js (135 lines)
+### src/ui/loop.js (136 lines)
 The frame loop and boot.
 - functions: scanVisible, frame, boot
 - variables: lastT, acc, lastRender, frameMs, simMs, fpsSm, ambientT

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: t67 phase 4, "doesn't connect" marks (Claude Code)
+
+- `nearMiss(bx, by, end, planned)` in `src/sim/joins.js`: an end with no join that would join
+  seamlessly, with a diagonal piece involved, one block up or down in empty space. Drop joins
+  count as connected; straight beside straight is never marked. It checks the moved block
+  through a small override view of `planned`, so ghost maps are never copied.
+- Marks: a red ring with a slash at the end, on built pieces and ghosts (`drawJoinMarks` in
+  `src/render/overlays.js`, called every frame from `src/ui/loop.js`) and at the ends of a drag
+  preview (`src/ui/previews.js`). Hover says "doesn't connect: place it one block higher/lower"
+  (`src/ui/info.js`). This covers t58's mark for belts and the same cases for screws.
+- Tests: 7 nearMiss checks in `test/t_joins.js`; `python3 test/run_all.py --browser` all passed.
+  `docs/PROJECT_MAP.md` regenerated.
+
 ## 2026-10-27: t67 phase 3 shared drag placement, and snapping (Claude Code)
 
 - `dragPlan(P, a, b, shift)` in `src/ui/selection.js` gives code, direction, variant, blocks and