Build range follows the screen; out-of-range replace ghosts replace (t64)

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

docs/DESIGN.md

@@ -470,7 +470,8 @@ above, including:
   building needs a range limit at all, since the bot needs no arms to build. Agreed: keep a limit,
   but make it about what's on screen, so anything the player can see and aim at builds directly
   and anything beyond stays a blueprint built when the bot comes near. No limit at all would let
-  players build in places they've never been and link far claims instantly. Not built yet.
+  players build in places they've never been and link far claims instantly. Built: the range is
+  the visible view box, at least 64 grains from its centre and at most 200 when zoomed far out.
 - **Sticky materials slide freely on built surfaces (t61, 2026-10-27).** Stickiness (STICK) is the
   chance per tick a grain takes a diagonal step, which made clay lumps, snow, wood chunks, ash and
   dirt creep down sloped walls (a single clay grain never got down a 20-piece slope). The owner

docs/PROJECT_MAP.md

@@ -315,9 +315,10 @@ Bars and other loose objects (ents), and the bag: adding, taking, costs and refu
 - functions: entSolidCell, entSupportCount, entFreeAt, entMark, spawnBar, removeEnt, entScrewAt, entScrewFree, entScrewMove, entScrewLane, entScrewEdge, entScrewEnter, entScrewTick, entDiagonalScrewTick, entBeltScrewEnter, entSlopeBeltTick, entTick, entsInCircle, bagAdd, bagTake, giveOrDrop, refundAt, canAfford, payCost, fmtMoney, costText, needText
 - variables: BAR_W, BAR_H, entCurM, droppedLast
 
-### src/sim/tools.js (52 lines)
+### src/sim/tools.js (65 lines)
 Tool helpers: reach, brushes, and plain digging.
-- functions: inReach, forBrush, drillReach, inDrillReach, toolDig
+- functions: setBuildRange, inBuildRange, inReach, forBrush, drillReach, inDrillReach, toolDig
+- variables: BUILD_MAX, buildBox
 
 ### src/sim/drill.js (161 lines)
 The resonance drill: tuned pulses that shatter one material.
@@ -342,7 +343,7 @@ Player actions on built things: take back, place a machine or mold, gates, F to
 Blueprints: copy, cut, flip, cost and paste (as ghosts) a region of built pieces.
 - functions: copyRegion, flipBlueprint, bpCost, pasteGhost, cutRegion, footprintBlocker, clearFootprint
 
-### src/sim/undo.js (87 lines)
+### src/sim/undo.js (93 lines)
 Undo (Ctrl+Z) for building, and the bot building ghosts.
 - functions: undoNote, undoPush, undoRecord, undoLast, clearAllGhosts, ghostTick, ghostTick0
 - variables: UNDO_MAX, undoStack, undoRec, ghostMissing, ghostIter
@@ -511,7 +512,7 @@ Keyboard and mouse listeners.
 - functions: isTyping
 - variables: canvas
 
-### src/ui/actions.js (242 lines)
+### src/ui/actions.js (243 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
@@ -544,7 +545,7 @@ 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 (136 lines)
+### src/ui/loop.js (137 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: t64 build range about the screen; out-of-range replace ghosts (Claude Code)
+
+- `setBuildRange`/`inBuildRange` in `src/sim/tools.js`: the UI sets the view box each frame
+  (`src/ui/loop.js`); half-sizes clamped to REACH..BUILD_MAX (64..200 grains); with no view (tests)
+  a REACH box around the bot. Used by `blockInReach`, machine/mold placement and previews,
+  right-click take-back, hover reach, and ghost building for blocks, machines and molds.
+- A replace (G) placed beyond range stores a replace flag on the ghost (`[code, v, extra, 1]`);
+  `ghostTick0` removes the old piece (refunded) and places the new one (charged), or re-sets a
+  filter's settings, when the bot comes in range.
+- Files: `src/sim/tools.js`, `src/sim/blocks.js`, `src/sim/undo.js`, `src/ui/actions.js`,
+  `src/ui/previews.js`, `src/ui/info.js`, `src/ui/loop.js`, `test/t_build.js`, `docs/DESIGN.md`,
+  `docs/PROJECT_MAP.md`. Tests: `python3 test/run_all.py --browser` all passed. Not played by hand.
+
 ## 2026-10-27: t49 throughput overlay (Claude Code)
 
 - The I overlay also shows grains per second at each line's open outlet, an orange glow on