beacon: add buy mode toggle (x1/x10/MAX) with B keyboard shortcut

The game had buyMode logic (1, 10, -1 for max) but zero UI to switch
between them. Players could only buy one building at a time.

Changes:
- Added x1/x10/MAX toggle buttons above the BUILDINGS section
- Active mode highlights in gold
- Press B to cycle through modes
- buyMode persists across saves
- Init log mentions the B shortcut

game.js

@@ -85,6 +85,7 @@ const G = {
     tick: 0,
     saveTimer: 0,
     secTimer: 0,
+    buyMode: 1, // 1, 10, or -1 (max)
 
     // Systems
     projects: [],
@@ -808,6 +809,42 @@ function getBuildingCost(id) {
     return cost;
 }
 
+function getBuildingBatchCost(id, count) {
+    const def = BDEF.find(b => b.id === id);
+    if (!def || count <= 0) return {};
+    const currentCount = G.buildings[id] || 0;
+    const cost = {};
+    for (let i = 0; i < count; i++) {
+        for (const [resource, amount] of Object.entries(def.baseCost)) {
+            cost[resource] = (cost[resource] || 0) + Math.floor(amount * Math.pow(def.costMult, currentCount + i));
+        }
+    }
+    return cost;
+}
+
+function getMaxBuyable(id) {
+    const def = BDEF.find(b => b.id === id);
+    if (!def) return 0;
+    // Simulate buying one at a time until we can't afford
+    let count = 0;
+    const tempResources = {};
+    for (const r of Object.keys(def.baseCost)) tempResources[r] = G[r] || 0;
+    const currentCount = G.buildings[id] || 0;
+    for (let i = 0; i < 1000; i++) { // cap at 1000
+        let canAfford = true;
+        for (const [resource, amount] of Object.entries(def.baseCost)) {
+            const cost = Math.floor(amount * Math.pow(def.costMult, currentCount + i));
+            if (tempResources[resource] < cost) { canAfford = false; break; }
+        }
+        if (!canAfford) break;
+        for (const [resource, amount] of Object.entries(def.baseCost)) {
+            tempResources[resource] -= Math.floor(amount * Math.pow(def.costMult, currentCount + i));
+        }
+        count++;
+    }
+    return count;
+}
+
 function canAffordBuilding(id) {
     const cost = getBuildingCost(id);
     for (const [resource, amount] of Object.entries(cost)) {
@@ -816,6 +853,16 @@ function canAffordBuilding(id) {
     return true;
 }
 
+function canAffordBatch(id) {
+    const count = G.buyMode === -1 ? getMaxBuyable(id) : G.buyMode;
+    if (count <= 0) return false;
+    const cost = getBuildingBatchCost(id, count);
+    for (const [resource, amount] of Object.entries(cost)) {
+        if ((G[resource] || 0) < amount) return false;
+    }
+    return true;
+}
+
 function spendBuilding(id) {
     const cost = getBuildingCost(id);
     for (const [resource, amount] of Object.entries(cost)) {
@@ -1045,15 +1092,26 @@ function checkProjects() {
 function buyBuilding(id) {
     const def = BDEF.find(b => b.id === id);
     if (!def || !def.unlock()) return;
-
     if (def.phase > G.phase + 1) return;
 
-    if (!canAffordBuilding(id)) return;
+    const buyCount = G.buyMode === -1 ? getMaxBuyable(id) : G.buyMode;
+    if (buyCount <= 0) return;
 
-    spendBuilding(id);
-    G.buildings[id] = (G.buildings[id] || 0) + 1;
+    if (buyCount === 1) {
+        if (!canAffordBuilding(id)) return;
+        spendBuilding(id);
+        G.buildings[id] = (G.buildings[id] || 0) + 1;
+        log(`Built ${def.name} (total: ${G.buildings[id]})`);
+    } else {
+        if (!canAffordBatch(id)) return;
+        const cost = getBuildingBatchCost(id, buyCount);
+        for (const [resource, amount] of Object.entries(cost)) {
+            G[resource] -= amount;
+        }
+        G.buildings[id] = (G.buildings[id] || 0) + buyCount;
+        log(`Built ${buyCount}x ${def.name} (total: ${G.buildings[id]})`);
+    }
     updateRates();
-    log(`Built ${def.name} (total: ${G.buildings[id]})`);
     render();
 }
 
@@ -1273,6 +1331,15 @@ function resolveAlignment(accept) {
 }
 
 // === ACTIONS ===
+function setBuyMode(mode) {
+    G.buyMode = mode;
+    // Update active button highlight
+    document.querySelectorAll('.buy-mode-btn').forEach(btn => {
+        btn.classList.toggle('active', parseInt(btn.dataset.mode) === mode);
+    });
+    renderBuildings();
+}
+
 function writeCode() {
     const base = 1;
     const bonus = Math.floor(G.buildings.autocoder * 0.5);
@@ -1643,7 +1710,7 @@ function saveGame() {
         branchProtectionFlag: G.branchProtectionFlag || 0, nightlyWatchFlag: G.nightlyWatchFlag || 0,
         nostrFlag: G.nostrFlag || 0,
         milestones: G.milestones, completedProjects: G.completedProjects, activeProjects: G.activeProjects,
-        totalClicks: G.totalClicks, startedAt: G.startedAt,
+        totalClicks: G.totalClicks, startedAt: G.startedAt, buyMode: G.buyMode,
         flags: G.flags,
         _seenBuildings: G._seenBuildings || [],
         _seenProjects: G._seenProjects || [],
@@ -1719,6 +1786,7 @@ function initGame() {
 
     log('The screen is blank. Write your first line of code.', true);
     log('Click WRITE CODE or press SPACE to start.');
+    log('Press B to toggle buy mode (x1 / x10 / MAX).');
     log('Build AutoCode for passive production.');
     log('Watch for Research Projects to appear.');
 }
@@ -1740,6 +1808,9 @@ window.addEventListener('load', function () {
         }
     }
 
+    // Restore buy mode button highlight
+    setBuyMode(G.buyMode || 1);
+
     // Game loop at 10Hz (100ms tick)
     setInterval(tick, 100);
 
@@ -1756,4 +1827,10 @@ window.addEventListener('keydown', function (e) {
         e.preventDefault();
         writeCode();
     }
+    if (e.code === 'KeyB' && e.target === document.body) {
+        e.preventDefault();
+        // Cycle: x1 -> x10 -> MAX -> x1
+        const next = G.buyMode === 1 ? 10 : G.buyMode === 10 ? -1 : 1;
+        setBuyMode(next);
+    }
 });

index.html

@@ -66,6 +66,8 @@ body{background:var(--bg);color:var(--text);font-family:'SF Mono','Cascadia Code
 .unlock-toast-item.building{border-color:#4a9eff;color:#4a9eff}
 .unlock-toast-item.project{border-color:#ffd700;color:#ffd700}
 .unlock-toast-item.milestone{border-color:#4caf50;color:#4caf50}
+.buy-mode-btn{min-width:36px}
+.buy-mode-btn.active{border-color:#ffd700!important;color:#ffd700!important;background:#1a1a08!important}
 </style>
 </head>
 <body>
@@ -103,6 +105,11 @@ body{background:var(--bg);color:var(--text);font-family:'SF Mono','Cascadia Code
 </div>
 <div id="alignment-ui" style="display:none"></div>
 <div id="events-ui" style="display:none"></div>
+<div id="buy-mode-toggle" style="display:flex;gap:4px;margin-bottom:8px">
+<button class="ops-btn buy-mode-btn active" onclick="setBuyMode(1)" data-mode="1">x1</button>
+<button class="ops-btn buy-mode-btn" onclick="setBuyMode(10)" data-mode="10">x10</button>
+<button class="ops-btn buy-mode-btn" onclick="setBuyMode(-1)" data-mode="-1">MAX</button>
+</div>
 <button class="save-btn" onclick="saveGame()">Save Game</button>
 <button class="reset-btn" onclick="if(confirm('Reset all progress?')){localStorage.removeItem('the-beacon-v2');location.reload()}">Reset Progress</button>
 <h2>BUILDINGS</h2>