Replace is held G instead of Ctrl (Ctrl+W/Ctrl+D were hit while flying)

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

docs/DESIGN.md

@@ -81,7 +81,7 @@ Details and numbers live in the code and in `docs/systems/`.
     leave one open block below and a belt under that carries them off. F is optional upkeep: it
     cleans the trough, chips off slag and rakes the furnace grate. Short stubs stay for the next
     firing.
-  - Build actions: drag for lines, Shift-drag for rectangles, Ctrl to replace, hold C / X and
+  - Build actions: drag for lines, Shift-drag for rectangles, hold G to replace, hold C / X and
     drag to copy / cut, V to paste, Ctrl+Z to undo, middle mouse to pick,
     Shift+Q/E to switch build tabs.
 - **Economy:**
@@ -123,7 +123,7 @@ above, including:
 - **Copy and cut** are held keys, not a tool. Hold C or X and drag a box; it acts on release.
   Copy and cut look different. Cut is destructive, but it can be pasted back or undone.
 - **Ctrl+Z undoes building** (up to 80 steps). The bot building ghosts is never a step of its own.
-- **Holding Ctrl** while placing replaces what is built there.
+- **Holding Ctrl** while placing replaces what is built there (moved to G on 2026-10-23).
 - **Fans melt like copper (1085°C).** Put the fan outside the furnace, blowing in through a grate.
   The game warns when a fan gets close to melting.
 - **The vacuum takes only ticked materials** when anything is ticked, even if the drag starts on
@@ -144,7 +144,7 @@ above, including:
   the load above it stands still and the belt slips underneath; the top no longer slides over
   a stuck bottom. Filters still let their chosen materials drop through.
 - **Pick** (middle mouse) selects the piece under the cursor with its direction,
-  wall material and filter settings. G is unbound, as the owner requested.
+  wall material and filter settings. G no longer picks, as the owner requested (it is now Replace).
 - **The build menu** is a bar of tabs and icon tiles along the bottom: Structure, Moving,
   Liquids, Machines, Molds. Hover a tile for its full description, cost and placement help;
   gamepad players see the selected tile’s popup. The top-left card is hidden while building,
@@ -165,6 +165,8 @@ above, including:
   players will do it only when they need more ore rather than more money.
 - The project moved from a claude.ai artifact to local development with coding agents. It is
   built from small files, with `NOTES.md` as the owner's to-do inbox.
+- **Replace is held G, not Ctrl.** The owner hit the browser's Ctrl+W (close tab) and Ctrl+D
+  (bookmark) while replacing and flying with WASD, and the game ignored WASD while Ctrl was held.
 
 ## Ideas not built yet
 

docs/PROJECT_MAP.md

@@ -406,7 +406,7 @@ The selected tool and piece: R / Q / E, drill width, filter picker, the selectio
 Discovery cards, hover info (I) and the cursor label.
 - functions: showCard, howText, discoveryCard, reactionsOf, hoverInfo, renderInfo, drawCursorLabel
 
-### src/ui/input.js (75 lines)
+### src/ui/input.js (79 lines)
 Keyboard and mouse listeners.
 - functions: isTyping
 - variables: canvas

docs/agent-log.md

@@ -4,6 +4,21 @@ 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.
 
+## 2026-10-23: Replace is held G, not Ctrl (Claude Code, with Codex)
+
+Note: "i see the issue was ctrl+w closing the tab… it happens for the bookmark hotkey too. maybe
+change the replace key?" The owner chose holding G.
+
+- `src/ui/input.js`: `GAME.ctrl` became `GAME.replace`, set while G is held. Ctrl no longer
+  does anything on its own, so WASD works while replacing. Ctrl+S, Ctrl+Z, Ctrl+wheel and the
+  leave-page prompt are unchanged.
+- Flag users and text: `previews.js`, `actions.js` ("Hold G to replace it."), `build-menu.js`
+  (Replace · G chip, key hints), `loop.js`, `state.js`, `notebook.js` controls, `docs/DESIGN.md`.
+- `test/play.py`: the replace checks hold G; a new check flies right with D while G is held
+  (121 checks pass). All 11 headless suites pass. `t_smooth.py`'s half-resolution check failed
+  on the slow fallback again (known, flaky under load).
+- Open: nothing.
+
 ## 2026-10-23: Ctrl+W no longer closes the game without asking (Claude Code)
 
 Note: "crash: hoplding crtl and pressing W crashes the whole browser."

src/ui/actions.js

@@ -137,15 +137,15 @@ function primaryPress(shift) {
       let err = '';
       undoRecord(rec => piecesIn(rec, 'block-') + piecesIn(rec, 'mach-') + piecesIn(rec, 'mold-') ? `replacing with a ${P.name.toLowerCase()}` : `placing a ${P.name.toLowerCase()}`, () => {
         err = check() || '';
-        // Ctrl: take down what you built in the way (refunded) and put this in its place
+        // G: take down what you built in the way (refunded) and put this in its place
-        if (err && GAME.ctrl && /already/.test(err)) {
+        if (err && GAME.replace && /already/.test(err)) {
           err = footprintBlocker(bx, by, bw, bh);
           if (!err && !canAfford(pieceCostNow(P), 1)) err = needText(pieceCostNow(P), 1);
           if (!err) err = clearFootprint(bx, by, bw, bh);
         }
         if (!err) err = place();
       });
-      if (err) { setStatus(err + (/already/.test(err) ? `${/[.!]$/.test(err) ? '' : '.'} Hold Ctrl to replace it.` : '')); playSfx('error'); } else { playSfx('place'); hudDirty = true; }
+      if (err) { setStatus(err + (/already/.test(err) ? `${/[.!]$/.test(err) ? '' : '.'} Hold G to replace it.` : '')); playSfx('error'); } else { playSfx('place'); hudDirty = true; }
     }
   }
 }
@@ -175,7 +175,7 @@ function primaryRelease(shift) {
     const near = list.filter(([bx, by]) => blockInReach(bx, by)), far = list.filter(([bx, by]) => !blockInReach(bx, by));
     let ghosts = 0;
     const r = undoRecord(rec => blockLabel(P, rec) + (piecesIn(rec, 'paste') ? ' (and its ghosts)' : ''), () => {
-      const res = placeBlocks(P.code, v, near, ex, GAME.ctrl);
+      const res = placeBlocks(P.code, v, near, ex, GAME.replace);
       const g = { t: 'paste', blocks: [], machines: [], molds: [] };
       for (const [bx, by] of far) {
         const b = by * BW + bx;
@@ -185,7 +185,7 @@ function primaryRelease(shift) {
       if (ghosts) undoNote(g);
       return res;
     });
-    const hint = /already built/.test(r.status) ? `${/[.!]$/.test(r.status) ? '' : '.'} Hold Ctrl to replace it.` : '';
+    const hint = /already built/.test(r.status) ? `${/[.!]$/.test(r.status) ? '' : '.'} Hold G to replace it.` : '';
     const gtxt = ghosts ? `${r.n ? `Placed ${plural(r.n, P.name.toLowerCase())}; ` : ''}${plural(ghosts, 'more')} out of reach ${ghosts === 1 ? 'is a ghost' : 'are ghosts'} your bot builds when it gets close.` : '';
     if (r.n || ghosts) { playSfx('place'); setStatus(gtxt || (r.status ? r.status + hint : ''), 'info'); } else { setStatus((r.status || 'Nothing placed.') + hint); playSfx('error'); }
     GAME.drag = null; GAME.dragDir = -1; hudDirty = true;

src/ui/build-menu.js

@@ -50,7 +50,7 @@ function renderBuildBar() {
   const status = performance.now() - GAME.statusT < 3200 ? GAME.status : '';
   const ng = ghostBlocks.size + ghostMachines.length + ghostMolds.length;
   const afford = ids.map(id => canAfford(pieceCostNow(PIECE_BY_ID[id]), 1) ? 1 : 0).join('');
-  const key = [cat, P.id, tip && tip.id, afford, GAME.wallMat, Math.round(money), GAME.ctrl, GAME.pieceDir[P.id], !!GAME.drag, GAME.dragDir, GAME.filterCfg.inv, GAME.filterCfg.m.join('.'), ng, ghostMissing, status, GAME.statusKind, innerWidth, innerHeight, SET.uiScale].join('|');
+  const key = [cat, P.id, tip && tip.id, afford, GAME.wallMat, Math.round(money), GAME.replace, GAME.pieceDir[P.id], !!GAME.drag, GAME.dragDir, GAME.filterCfg.inv, GAME.filterCfg.m.join('.'), ng, ghostMissing, status, GAME.statusKind, innerWidth, innerHeight, SET.uiScale].join('|');
   if (key === lastBuildKey) return;
   lastBuildKey = key;
   let h = '<div class="bb-head">' + BUILD_CATS.map(([name], k) => `<button class="bb-tab${k === cat ? ' on' : ''}" data-cat="${k}">${esc(name)}</button>`).join('')
@@ -74,7 +74,7 @@ function renderBuildBar() {
   const variant = pieceUsesWall(P) ? `<span class="chip hot"><span class="sw" style="display:inline-block;vertical-align:-2px;width:9px;height:9px;margin-right:4px;background:${rgbOf(WALL_OF[GAME.wallMat])}"></span>${esc(MD[WALL_OF[GAME.wallMat]].name.toLowerCase())} · R</span>`
     : P.filter ? `<span class="chip hot">${fc.inv ? 'carries' : 'drops'} ${fc.m.length ? sws(fc.m) : 'nothing'} · F</span>${dirChip}`
     : dir ? dirChip : '';
-  bar.querySelector('.bb-status').innerHTML = variant + (GAME.ctrl ? '<span class="chip hot">Replace · Ctrl</span>' : '')
+  bar.querySelector('.bb-status').innerHTML = variant + (GAME.replace ? '<span class="chip hot">Replace · G</span>' : '')
     + (ng ? `<span class="chip ok">${ng} ghost pieces waiting${ghostMissing ? ', some short on materials' : ''}.</span>` : '')
     + (status ? `<span class="chip ${GAME.statusKind === 'info' ? 'ok' : 'bad'}">${esc(status)}</span>` : '');
   const pop = $('bb-pop'); pop.hidden = !tip;
@@ -83,7 +83,7 @@ function renderBuildBar() {
   pop.innerHTML = `<div class="bb-title">${pieceIcon(tip.id)}<b>${esc(tip.name)}</b></div><div class="bb-chips">${chipCost(pieceCostNow(tip))}<span class="chip">${size}</span>${tip.power ? `<span class="chip">${tip.power} power</span>` : ''}</div>
     <div class="bb-desc">${esc(tip.desc)}</div><div class="bb-place"><b>How to place</b> ${tip.kind === 'block' ? 'Drag for a line, Shift-drag for a rectangle; out of reach becomes ghosts.' : 'Click to place.'}${tip.dirs && tip.kind === 'block' ? ' A dragged line runs the way you drag it; a single click uses <kbd>R</kbd>.' : tip.dirs ? ' <kbd>R</kbd> turns it.' : pieceUsesWall(tip) ? ' <kbd>R</kbd> picks the material.' : ''}</div>
     ${tip.filter ? `<div class="bb-place">New ones will ${esc(filterSentence(GAME.filterCfg))}. <kbd>F</kbd> sets materials and mode (or click materials in the bag, or <kbd>T</kbd> over one); <kbd>F</kbd> on a placed filter changes its whole row.</div>` : ''}
-    <div class="bb-place"><kbd>Ctrl</kbd> replace · <kbd>Ctrl</kbd>+<kbd>Z</kbd> undo · right click take back · middle mouse pick · hold <kbd>C</kbd>/<kbd>X</kbd> copy/cut · <kbd>V</kbd> paste</div>`;
+    <div class="bb-place">hold <kbd>G</kbd> replace · <kbd>Ctrl</kbd>+<kbd>Z</kbd> undo · right click take back · middle mouse pick · hold <kbd>C</kbd>/<kbd>X</kbd> copy/cut · <kbd>V</kbd> paste</div>`;
   const tile = bar.querySelector(`[data-piece="${tip.id}"]`); if (!tile) { pop.hidden = true; return; }
   const r = tile.getBoundingClientRect(), br = bar.getBoundingClientRect(), w = pop.getBoundingClientRect().width;
   pop.style.left = `${Math.max(8, Math.min(innerWidth - w - 8, r.left + r.width / 2 - w / 2)) - br.left}px`;

src/ui/input.js

@@ -11,7 +11,6 @@ window.addEventListener('keydown', e => {
     return;
   }
   if (!GAME.running) return;
-  if (e.key === 'Control') { GAME.ctrl = true; return; }
   if (e.ctrlKey || e.metaKey) {
     if (k === 's') { e.preventDefault(); saveWorld('main'); }
     else if (k === 'z' && !e.shiftKey) { e.preventDefault(); doUndo(); }
@@ -30,6 +29,7 @@ window.addEventListener('keydown', e => {
     case 'r': rotate(); break;
     case 't': if (toolId() === 'vacuum') toggleCollectUnderCursor(); else if (toolId() === 'build' && piece().filter) pickFilterUnderCursor(); break;
     case 'f': doInteract(); break;
+    case 'g': GAME.replace = true; hudDirty = true; break;
     case 'h': toggleLens(); break;
     case 'i': GAME.infoOverlay = !GAME.infoOverlay; playSfx('ui'); toast(GAME.infoOverlay ? 'Info overlay on: what every filter does, and which way belts and tubes run. I hides it.' : 'Info overlay off.'); break;
     case 'l': bot.lamp = !bot.lamp; playSfx('ui'); break;
@@ -43,9 +43,9 @@ window.addEventListener('keydown', e => {
     case 'Tab': $('bagpanel').hidden = !$('bagpanel').hidden; break;
   }
 });
-window.addEventListener('keyup', e => { const k = e.key.length === 1 ? e.key.toLowerCase() : e.key; keys.delete(k); if (e.key === 'Control') GAME.ctrl = false; if (k === 'c' || k === 'x') hudDirty = true; });
+window.addEventListener('keyup', e => { const k = e.key.length === 1 ? e.key.toLowerCase() : e.key; keys.delete(k); if (k === 'g') { GAME.replace = false; hudDirty = true; } if (k === 'c' || k === 'x') hudDirty = true; });
-window.addEventListener('blur', () => { keys.clear(); GAME.lmb = GAME.rmb = false; GAME.ctrl = false; GAME.selDrag = null; endRmbRecord(); });
+window.addEventListener('blur', () => { keys.clear(); GAME.lmb = GAME.rmb = false; GAME.replace = false; GAME.selDrag = null; endRmbRecord(); });
-canvas.addEventListener('mousemove', e => { GAME.ctrl = e.ctrlKey; GAME.mouse.x = e.clientX; GAME.mouse.y = e.clientY; GAME.mouse.in = true; if (GAME.usingPad) { GAME.usingPad = false; canvas.classList.remove('nocursor'); } });
+canvas.addEventListener('mousemove', e => { GAME.mouse.x = e.clientX; GAME.mouse.y = e.clientY; GAME.mouse.in = true; if (GAME.usingPad) { GAME.usingPad = false; canvas.classList.remove('nocursor'); } });
 canvas.addEventListener('mouseleave', () => { GAME.mouse.in = false; });
 canvas.addEventListener('contextmenu', e => e.preventDefault());
 canvas.addEventListener('mousedown', e => {
@@ -57,7 +57,7 @@ canvas.addEventListener('mousedown', e => {
   else if (e.button === 1) { e.preventDefault(); pickUnderCursor(); }
 });
 window.addEventListener('mouseup', e => {
-  if (e.button === 0) { GAME.ctrl = e.ctrlKey; if (GAME.lmb) primaryRelease(modShift()); GAME.lmb = false; }
+  if (e.button === 0) { if (GAME.lmb) primaryRelease(modShift()); GAME.lmb = false; }
   else if (e.button === 2) { GAME.rmb = false; endRmbRecord(); }
 });
 canvas.addEventListener('wheel', e => {
@@ -74,6 +74,6 @@ document.addEventListener('visibilitychange', () => {
   if (document.hidden) { if (SET.muteUnfocused) AU.ctx.suspend(); }
   else AU.ctx.resume();
 });
-// Ctrl+W closes the tab and the page cannot stop it, and Ctrl (replace) + W (fly) is an easy slip:
+// Ctrl+W closes the tab and the page cannot stop it:
 // while a world is open, ask the browser to confirm leaving
 window.addEventListener('beforeunload', e => { if (GAME.running) { e.preventDefault(); e.returnValue = ''; } });

src/ui/loop.js

@@ -74,7 +74,7 @@ function frame(now) {
   drawRain();
   drawBot();
   if (!GAME.hidePreviews) drawPreviews(); // tools/shot.py hides them for clean screenshots
-  if (GAME.ctrl !== GAME.ctrlShown) { GAME.ctrlShown = GAME.ctrl; hudDirty = true; }
+  if (GAME.replace !== GAME.replaceShown) { GAME.replaceShown = GAME.replace; hudDirty = true; }
   renderBuildBar();
   if (hudDirty || R.frame % 6 === 0) { renderSelCard(); renderBag(); renderWallet(); hudDirty = false; }
   if (R.frame % 4 === 0) renderInfo();

src/ui/notebook.js

@@ -171,7 +171,7 @@ function controlsHtml() {
     ['Fly', 'W A S D'], ['Boost while flying', 'Shift'], ['Tool modifier (while not flying)', 'Shift'], ['Use tool', 'Left mouse'], ['Second action', 'Right mouse'],
     ['Tools', '1 – 4'], ['Cycle what you blow · piece', 'Q / E'], ['Switch build tab', 'Shift + Q / E'], ['Variant: material · direction · flip', 'R'],
     ['Tick/untick what is under the cursor (Vacuum)', 'R or T'], ['Nozzle or brush size', '[ ]  or  Shift + wheel'],
-    ['Replace what is built (Build)', 'Hold Ctrl'], ['Copy a box of what you built', 'Hold C, drag'], ['Cut a box (refunded, paste it back)', 'Hold X, drag'], ['Paste again', 'V'], ['Undo building', 'Ctrl + Z'], ['Blueprint library', 'B'], ['Zoom', 'Mouse wheel'], ['Interact (gates, molds, fans, filters)', 'F'], ['Thermal lens', 'H'], ['Info overlay: filters, belt and tube directions', 'I'], ['Bot lamp', 'L'],
+    ['Replace what is built (Build)', 'Hold G'], ['Copy a box of what you built', 'Hold C, drag'], ['Cut a box (refunded, paste it back)', 'Hold X, drag'], ['Paste again', 'V'], ['Undo building', 'Ctrl + Z'], ['Blueprint library', 'B'], ['Zoom', 'Mouse wheel'], ['Interact (gates, molds, fans, filters)', 'F'], ['Thermal lens', 'H'], ['Info overlay: filters, belt and tube directions', 'I'], ['Bot lamp', 'L'],
     ['Pick the piece under the cursor (with its direction and settings)', 'Middle mouse'], ['Notebook', 'N'], ['Clear all blueprint ghosts', 'Delete'], ['Save', 'Ctrl + S'], ['Pause · menu', 'Esc'], ['Mute', 'M'],
   ];
   const pad = [

src/ui/previews.js

@@ -176,7 +176,7 @@ function drawPreviews() {
       const afford = canAfford(pieceCostNow(P), cells.length);
       for (const [bx, by] of cells) {
         const err = canPlaceBlock(bx, by), rb = by * BW + bx;
-        const swap = GAME.ctrl && !!blockP[rb] && /already built/.test(err) && !blockIs(rb, P.code, v, pieceExtra(P));
+        const swap = GAME.replace && !!blockP[rb] && /already built/.test(err) && !blockIs(rb, P.code, v, pieceExtra(P));
         const ghost = !blockInReach(bx, by) && (!err || /bar/.test(err)); // out of reach: it will be a ghost
         const ok = (!err || swap) && !ghost && afford;
         const [x, y, w, h] = blockRectPx(bx, by, 1, 1);
@@ -217,7 +217,7 @@ function drawPreviews() {
       const bw = P.kind === 'mold' ? MOLDS[P.mold].bw : P.bw, bh = P.kind === 'mold' ? MOLDS[P.mold].bh : P.bh;
       const { bx, by } = stampOrigin(bw, bh);
       const err = P.kind === 'mold' ? canPlaceMold(P.mold, bx, by) : canPlaceMachine(P.id, bx, by);
-      const swap = !!err && GAME.ctrl && /already/.test(err) && !footprintBlocker(bx, by, bw, bh);
+      const swap = !!err && GAME.replace && /already/.test(err) && !footprintBlocker(bx, by, bw, bh);
       const ok = (!err || swap) && inReach(bx * BS + bw * BS / 2, by * BS + bh * BS / 2) && canAfford(pieceCostNow(P), 1);
       const [x, y, w, h] = blockRectPx(bx, by, bw, bh);
       if (swap && ok) { ctx.fillStyle = 'rgba(255,190,90,0.35)'; ctx.fillRect(x, y, w, h); }
@@ -250,7 +250,7 @@ function drawPreviews() {
     ctx.beginPath(); ctx.moveTo(cx - 10, cy); ctx.lineTo(cx - 4, cy); ctx.moveTo(cx + 4, cy); ctx.lineTo(cx + 10, cy); ctx.moveTo(cx, cy - 10); ctx.lineTo(cx, cy - 4); ctx.moveTo(cx, cy + 4); ctx.lineTo(cx, cy + 10); ctx.stroke();
   }
   ctx.restore();
-  if (t === 'build' && GAME.ctrl && !sel && !pasting) drawTag('Replace', '255,190,90', p.x + BS * zp * 1.2, p.y + BS * zp * 1.4);
+  if (t === 'build' && GAME.replace && !sel && !pasting) drawTag('Replace', '255,190,90', p.x + BS * zp * 1.2, p.y + BS * zp * 1.4);
   drawCursorLabel(p.x, p.y, t === 'vacuum' ? GAME.brush[GAME.tool] : t === 'ignite' || t === 'drill' ? 1 : 2);
 }
 // a small labelled tag drawn on the world (screen pixels)

src/ui/state.js

@@ -40,7 +40,7 @@ function loadCollect() { try { const a = JSON.parse(localStorage.getItem('deepgr
 const GAME = {
   running: false, paused: false, tool: 0, dropMat: 0, matChosen: false, wallMat: RSTONE, filterCfg: { m: [], inv: 0 }, pieceIdx: 0, pieceDir: {},
   brush: [3, 2, 0, 0, 0], collect: loadCollect(), tipsOpen: new Set(), cards: [], vacFilter: 0, vacLocked: false, rmbConsumed: false, rmbSeen: new Set(), lookHold: { x: 0, y: 0 },
-  paste: false, selDrag: null, rmbRec: null, dragDir: -1, ctrlShown: false, clip: null, drag: null, aim: { x: 0, y: 0 }, mouse: { x: 0, y: 0, in: false },
+  paste: false, selDrag: null, rmbRec: null, dragDir: -1, replaceShown: false, clip: null, drag: null, aim: { x: 0, y: 0 }, mouse: { x: 0, y: 0, in: false },
   lmb: false, rmb: false, blowMix: false, drillW: 1, drillTune: 0, lastDug: 0, padRun: 0, status: '', statusKind: 'err', statusT: 0, usingPad: false, padAim: { x: 12, y: 0 },
   lastAutosave: 0, playTime: 0, lastHud: 0, worldName: '',
 };

test/play.py

@@ -27,7 +27,7 @@ with sync_playwright() as p:
     ev = pg.evaluate
     look = sys.argv[2] if len(sys.argv) > 2 else 'pixel'
     check('a new game starts fully zoomed in', ev('SET.zoom') == 12, ev('SET.zoom'))
-    # Ctrl+W (Ctrl to replace, W to fly) closes the tab; with a world open the browser must ask first
+    # Ctrl+W closes the tab; with a world open the browser must ask first
     leave = "(() => { const e = new Event('beforeunload', { cancelable: true }); dispatchEvent(e); return e.defaultPrevented; })()"
     check('leaving the page with a world open asks to confirm', ev(leave))
     check('but not on the title screen', not ev(f'(() => {{ GAME.running = false; const r = {leave}; GAME.running = true; return r; }})()'))
@@ -339,16 +339,21 @@ with sync_playwright() as p:
     pg.keyboard.press('Escape'); settle(100)
     pg.keyboard.press('Control+z'); settle(300)
     check('Ctrl+Z puts the cut row back', ev(f'blockP[({bby} + 1) * BW + {bbx} - 4]') == ev('BP_BELT') and ev('money') == m_before, ev('[money, GAME.status]'))
-    # Ctrl with a machine: it replaces the belt it is placed on
+    # G with a machine: it replaces the belt it is placed on
     ok = select('3', "piece().id === 'fan'")
     pg.mouse.move(*blk(bbx - 4, bby + 1)); settle(400)
     pg.mouse.down(); pg.mouse.up(); settle(100)
-    check('a fan on a belt says to hold Ctrl', 'Ctrl' in ev('GAME.status'), ev('GAME.status'))
+    check('a fan on a belt says to hold G', 'Hold G' in ev('GAME.status'), ev('GAME.status'))
-    pg.keyboard.down('Control'); settle(100); pg.mouse.move(*blk(bbx - 4, bby + 1)); settle(200)
+    pg.keyboard.down('g'); settle(100); pg.mouse.move(*blk(bbx - 4, bby + 1)); settle(200)
-    check('holding Ctrl shows replace mode', 'Replace' in ev("$('buildbar').textContent"))
+    check('holding G shows replace mode', 'Replace' in ev("$('buildbar').textContent"))
     pg.screenshot(path=str(out / '07g-replace-fan.png'))
-    pg.mouse.down(); pg.mouse.up(); settle(100); pg.keyboard.up('Control'); settle(100)
+    pg.mouse.down(); pg.mouse.up(); settle(100); pg.keyboard.up('g'); settle(100)
-    check('Ctrl-click puts the fan in place of the belt', ev(f"machines.some(m => m && m.type === 'fan' && m.x === ({bbx} - 4) * 4 && m.y === ({bby} + 1) * 4)") and ev(f'blockP[({bby} + 1) * BW + {bbx} - 4]') == 0, ev('GAME.status'))
+    check('G-click puts the fan in place of the belt', ev(f"machines.some(m => m && m.type === 'fan' && m.x === ({bbx} - 4) * 4 && m.y === ({bby} + 1) * 4)") and ev(f'blockP[({bby} + 1) * BW + {bbx} - 4]') == 0, ev('GAME.status'))
+    x_before, y_before = ev('[bot.x, bot.y]')
+    pg.keyboard.down('g'); pg.keyboard.down('d'); settle(300)
+    pg.keyboard.up('d'); pg.keyboard.up('g')
+    check('flying with WASD works while G (replace) is held', ev('bot.x') > x_before, ev('bot.x') - x_before)
+    ev(f'bot.x = {x_before}; bot.y = {y_before}; R.snapNext = true;'); settle(200)
     # pipes are laid by dragging, like belts
     ok = select('3', "piece().id === 'pipe'")
     check('pipes, pumps, outlets and the refiner are in the build menu', ok and all(x in ev("PIECES.filter(p => !p.hidden).map(p => p.id)") for x in ['pipe', 'pump', 'outlet', 'refiner']))
@@ -360,7 +365,7 @@ with sync_playwright() as p:
     pg.keyboard.press('Control+z'); settle(200)
     check('and Ctrl+Z swaps the belt back', ev(f'blockP[({bby} + 1) * BW + {bbx} - 4]') == ev('BP_BELT') and not ev(f"machines.some(m => m && m.type === 'fan' && m.x === ({bbx} - 4) * 4)"), ev('GAME.status'))
 
-    # 7b. filter: choose several materials with F, place a line, replace belts with Ctrl, edit the whole line
+    # 7b. filter: choose several materials with F, place a line, replace belts with G, edit the whole line
     ev('seen[CUORE] = 1; seen[FEORE] = 1; seen[SAND] = 1; money = 1000; GAME.filterCfg = { m: [], inv: 0 };')
     ok = select('3', "piece().id === 'filter'")
     check('select filter', ok)
@@ -375,16 +380,16 @@ with sync_playwright() as p:
     drag(lambda: blk(bbx - 6, fy), lambda: blk(bbx - 3, fy))
     nf = ev('blockP.reduce((a, v) => a + (v === BP_FILTER), 0)')
     check('filters placed by drag, dropping both ores and carrying right', nf == 4 and ev(f'blockV[{fy}*BW+{bbx-5}]') == 128 and ev(f'filterInfo({fy}*BW+{bbx-5}).m.length') == 2, f"{nf} {ev(f'JSON.stringify(filterInfo({fy}*BW+{bbx-5}))')}")
-    # two belts at the end of the line: plain dragging leaves them, Ctrl-dragging swaps them for filters
+    # two belts at the end of the line: plain dragging leaves them, G-dragging swaps them for filters
     ev(f"placeBlock(BP_BELT, 1, {bbx-2}, {fy}, true); placeBlock(BP_BELT, 1, {bbx-1}, {fy}, true);")
     drag(lambda: blk(bbx - 2, fy), lambda: blk(bbx - 1, fy))
-    check('dragging over built belts leaves them and says how to replace', ev(f'blockP[{fy}*BW+{bbx-2}] === BP_BELT') and 'Ctrl' in ev('GAME.status'), ev('GAME.status'))
+    check('dragging over built belts leaves them and says how to replace', ev(f'blockP[{fy}*BW+{bbx-2}] === BP_BELT') and 'Hold G' in ev('GAME.status'), ev('GAME.status'))
-    pg.keyboard.down('Control'); settle(50)
+    pg.keyboard.down('g'); settle(50)
     pg.mouse.move(*blk(bbx - 2, fy)); settle(300)
     pg.screenshot(path=str(out / '07c-replace-preview.png'))
     drag(lambda: blk(bbx - 2, fy), lambda: blk(bbx - 1, fy))
-    pg.keyboard.up('Control'); settle(50)
+    pg.keyboard.up('g'); settle(50)
-    check('Ctrl-dragging replaces them with filters', ev(f'blockP[{fy}*BW+{bbx-2}] === BP_FILTER && blockP[{fy}*BW+{bbx-1}] === BP_FILTER') and ev(f'filterRun({fy}*BW+{bbx-5}).length') == 6, ev('GAME.status'))
+    check('G-dragging replaces them with filters', ev(f'blockP[{fy}*BW+{bbx-2}] === BP_FILTER && blockP[{fy}*BW+{bbx-1}] === BP_FILTER') and ev(f'filterRun({fy}*BW+{bbx-5}).length') == 6, ev('GAME.status'))
     pg.mouse.move(*blk(bbx - 5, fy)); settle(200)
     check('hovering a filter says what it drops and carries', 'copper ore' in ev('JSON.stringify(hoverInfo(Math.floor(GAME.aim.x), Math.floor(GAME.aim.y)))').lower())
     ev(f"for (let y = {fy*4 - 10}; y < {fy*4 - 1}; y++) for (let x = {(bbx-6)*4}; x < {(bbx-5)*4 + 2}; x++) setCell(y*W+x, [SAND, CUORE, FEORE][(x+y)%3], 20, 0);")