feat: buy x1/x5/x10/xMax + production preview per generator

- buyGenerator() supports quantity param (multi-buy loop)
- maxAffordable() / bulkCost() — compute max purchasable + total cost
- GeneratorShop: mode selector (x1/x5/x10/MAX)
- Each generator shows +X/s in amber — what the next purchase adds
- Button shows total cost + quantity (e.g. "1.5k (x5)")

Frontend/src/lib/components/GeneratorShop.svelte

@@ -2,9 +2,14 @@
 	import { scale } from 'svelte/transition';
 	import { quintOut } from 'svelte/easing';
 	import { game } from '$lib/stores/game.svelte';
-	import { generatorEffectiveProduction } from '$lib/core/economy';
+	import { generatorEffectiveProduction, maxAffordable, bulkCost } from '$lib/core/economy';
 	import { formatNumber } from '$lib/utils/formatNumber';
 	import CollapsiblePanel from './CollapsiblePanel.svelte';
+
+	type BuyMode = 1 | 5 | 10 | 'max';
+	let buyMode = $state<BuyMode>(1);
+
+	const MODES: BuyMode[] = [1, 5, 10, 'max'];
 </script>
 
 <CollapsiblePanel
@@ -12,11 +17,28 @@
 	badge="{formatNumber(game.productionPerSecond)}/s"
 	accentClass=""
 >
+	<!-- Buy mode selector -->
+	<div class="flex gap-0.5 p-0.5 rounded-lg" style="background: rgba(255,255,255,0.04);">
+		{#each MODES as mode}
+			<button
+				class="flex-1 py-1 rounded-md text-[0.65rem] font-semibold transition-all duration-150"
+				style="font-family: var(--font); {buyMode === mode
+					? 'background: rgba(255,255,255,0.1); color: rgba(255,255,255,0.95);'
+					: 'background: transparent; color: rgba(255,255,255,0.4);'
+				}"
+				onclick={() => buyMode = mode}
+			>
+				{mode === 'max' ? 'MAX' : `x${mode}`}
+			</button>
+		{/each}
+	</div>
+
 	{#each game.state.generators as gen, i}
-		{@const cost = game.generatorCostWithTree(gen)}
-		{@const canAfford = game.state.resources >= cost}
+		{@const qty = buyMode === 'max' ? maxAffordable(game.state, gen.id) : buyMode}
+		{@const cost = qty <= 1 ? game.generatorCostWithTree(gen) : bulkCost(game.state, gen.id, qty)}
+		{@const canAfford = game.state.resources >= cost && qty > 0}
 		{@const effectiveProd = generatorEffectiveProduction(gen, game.state)}
-		{@const nextUnitProd = generatorEffectiveProduction({ ...gen, owned: 1 }, game.state)}
+		{@const nextGain = generatorEffectiveProduction({ ...gen, owned: qty || 1 }, game.state)}
 		{@const share = game.productionPerSecond > 0 ? (effectiveProd / game.productionPerSecond * 100) : 0}
 		<div
 			class="gp-row {canAfford ? 'gp-row--active' : 'gp-row--locked'}"
@@ -39,21 +61,30 @@
 						<span class="gp-label gp-accent-green">{formatNumber(effectiveProd)}/s</span>
 						<span class="gp-label">·</span>
 						<span class="gp-label">{share.toFixed(0)}%</span>
+						<span class="gp-label">·</span>
+						<span class="gp-label gp-accent-amber">+{formatNumber(nextGain)}/s</span>
 					</div>
-					<!-- Mini progress showing share of total production -->
 					<div class="h-[2px] rounded-full mt-0.5" style="background: rgba(255,255,255,0.06);">
 						<div class="h-full rounded-full" style="width: {Math.min(share, 100)}%; background: var(--color-gp-accent-green); opacity: 0.5;"></div>
 					</div>
 				{:else}
-					<span class="gp-label">+{formatNumber(nextUnitProd)}/s par unite</span>
+					<span class="gp-label">
+						<span class="gp-accent-amber">+{formatNumber(nextGain)}/s</span> par unite
+					</span>
 				{/if}
 			</div>
 			<button
-				onclick={() => game.buy(gen.id)}
+				onclick={() => game.buy(gen.id, qty || 1)}
 				disabled={!canAfford}
 				class="gp-btn {canAfford ? 'gp-btn--buy' : 'gp-btn--disabled'}"
 			>
+				{#if buyMode === 'max' && qty > 1}
+					{formatNumber(cost)} (x{qty})
+				{:else if buyMode !== 1 && buyMode !== 'max'}
+					{formatNumber(cost)} (x{buyMode})
+				{:else}
 					{formatNumber(cost)}
+				{/if}
 			</button>
 		</div>
 	{/each}

Frontend/src/lib/core/economy.ts

@@ -661,22 +661,62 @@ export function applyClick(state: GameState, rng: number = Math.random()): Click
 }
 
 // Achat d'un générateur (retourne null si fonds insuffisants)
-export function buyGenerator(state: GameState, genId: string): GameState | null {
+export function buyGenerator(state: GameState, genId: string, quantity = 1): GameState | null {
   const genIndex = state.generators.findIndex((g) => g.id === genId);
   if (genIndex === -1) return null;
 
-  const gen = state.generators[genIndex];
+  let gen = { ...state.generators[genIndex] };
+  let resources = state.resources;
+
+  let bought = 0;
+  for (let i = 0; i < quantity; i++) {
     const cost = generatorCost(gen, state.evolutionTree);
-  if (state.resources < cost) return null;
+    if (resources < cost) break;
+    resources -= cost;
+    gen = { ...gen, owned: gen.owned + 1 };
+    bought++;
+  }
+
+  if (bought === 0) return null;
 
   const updatedGenerators = [...state.generators];
-  updatedGenerators[genIndex] = { ...gen, owned: gen.owned + 1 };
+  updatedGenerators[genIndex] = gen;
 
-  return {
-    ...state,
-    resources: state.resources - cost,
-    generators: updatedGenerators,
-  };
+  return { ...state, resources, generators: updatedGenerators };
+}
+
+// Calcule combien d'unités on peut acheter avec les ressources actuelles
+export function maxAffordable(state: GameState, genId: string): number {
+  const genIndex = state.generators.findIndex((g) => g.id === genId);
+  if (genIndex === -1) return 0;
+
+  let gen = { ...state.generators[genIndex] };
+  let resources = state.resources;
+  let count = 0;
+
+  while (true) {
+    const cost = generatorCost(gen, state.evolutionTree);
+    if (resources < cost) break;
+    resources -= cost;
+    gen = { ...gen, owned: gen.owned + 1 };
+    count++;
+    if (count > 1000) break; // safety
+  }
+  return count;
+}
+
+// Cout total pour acheter N unités
+export function bulkCost(state: GameState, genId: string, quantity: number): number {
+  const genIndex = state.generators.findIndex((g) => g.id === genId);
+  if (genIndex === -1) return Infinity;
+
+  let gen = { ...state.generators[genIndex] };
+  let total = 0;
+  for (let i = 0; i < quantity; i++) {
+    total += generatorCost(gen, state.evolutionTree);
+    gen = { ...gen, owned: gen.owned + 1 };
+  }
+  return total;
 }
 
 // Prestige : reset run, gain ADN, arbre persiste

Frontend/src/lib/stores/game.svelte.ts

@@ -127,9 +127,9 @@ class Game {
 		this.lastClickCrit = result.isCrit;
 	}
 
-	buy(genId: string) {
+	buy(genId: string, quantity = 1) {
 		if (!this.ready) return;
-		const updated = buyGenerator(applyIdleGains(this.state, Date.now()), genId);
+		const updated = buyGenerator(applyIdleGains(this.state, Date.now()), genId, quantity);
 		if (updated) this.applyState(updated);
 	}