feat(app): 主页新增难度选择UI，游戏页读取localStorage难度参数

app/page.tsx

@@ -1,6 +1,7 @@
 'use client'
 
-import Link from 'next/link'
+import { useState } from 'react'
+import { useRouter } from 'next/navigation'
 
 // 背景装饰黑话词条
 const BUZZ_WORDS = [
@@ -11,7 +12,53 @@ const BUZZ_WORDS = [
   '向上管理', '自驱力', '全链路', '数据驱动', '业务增长',
 ]
 
+type DifficultyLevel = 'easy' | 'normal' | 'hard'
+
+const DIFFICULTY_OPTIONS: {
+  key: DifficultyLevel
+  label: string
+  desc: string
+  color: string
+  borderColor: string
+  glowColor: string
+}[] = [
+  {
+    key: 'easy',
+    label: '简单',
+    desc: '带薪摸鱼，准点下班',
+    color: '#22C55E',
+    borderColor: '#16a34a',
+    glowColor: 'rgba(34,197,94,0.35)',
+  },
+  {
+    key: 'normal',
+    label: '普通',
+    desc: '常规打工，偶有加班',
+    color: '#3B82F6',
+    borderColor: '#2563eb',
+    glowColor: 'rgba(59,130,246,0.35)',
+  },
+  {
+    key: 'hard',
+    label: '困难',
+    desc: '地狱模式，007全开',
+    color: '#EF4444',
+    borderColor: '#dc2626',
+    glowColor: 'rgba(239,68,68,0.35)',
+  },
+]
+
 export default function GameCover() {
+  const [selectedDifficulty, setSelectedDifficulty] = useState<DifficultyLevel>('normal')
+  const router = useRouter()
+
+  const handleStart = () => {
+    if (typeof window !== 'undefined') {
+      localStorage.setItem('game-difficulty', selectedDifficulty)
+    }
+    router.push('/game')
+  }
+
   return (
     <main
       className="crt-overlay relative w-full min-h-screen flex flex-col items-center justify-center overflow-hidden"
@@ -22,7 +69,7 @@ export default function GameCover() {
         backgroundPosition: 'center',
       }}
     >
-      {/* 深色叠加层，确保文字可读 */}
+      {/* 深色叠加层 */}
       <div className="absolute inset-0" style={{ backgroundColor: 'rgba(10,10,30,0.72)' }} />
 
       {/* CRT 流动扫描线 */}
@@ -108,9 +155,54 @@ export default function GameCover() {
           部署打工人防线，捍卫最后的 HC
         </p>
 
+        {/* 难度选择 */}
+        <div className="w-full">
+          <p
+            className="font-pixel text-center mb-3"
+            style={{ fontSize: '9px', color: '#7C3AED', letterSpacing: '0.2em' }}
+          >
+            选择难度
+          </p>
+          <div className="flex gap-3 justify-center">
+            {DIFFICULTY_OPTIONS.map(opt => {
+              const isSelected = selectedDifficulty === opt.key
+              return (
+                <button
+                  key={opt.key}
+                  onClick={() => setSelectedDifficulty(opt.key)}
+                  style={{
+                    flex: 1,
+                    padding: '10px 8px',
+                    backgroundColor: isSelected ? `rgba(${opt.key === 'easy' ? '34,197,94' : opt.key === 'normal' ? '59,130,246' : '239,68,68'},0.15)` : '#0F1B2D',
+                    border: `2px solid ${isSelected ? opt.color : '#1e3a5f'}`,
+                    borderRadius: '10px',
+                    cursor: 'pointer',
+                    transition: 'all 0.15s ease',
+                    boxShadow: isSelected ? `0 0 16px ${opt.glowColor}` : 'none',
+                    transform: isSelected ? 'translateY(-2px)' : 'none',
+                  }}
+                >
+                  <div
+                    className="font-vt323"
+                    style={{ fontSize: '22px', color: opt.color, marginBottom: '2px' }}
+                  >
+                    {opt.label}
+                  </div>
+                  <div
+                    className="font-vt323"
+                    style={{ fontSize: '13px', color: '#9CA3AF', lineHeight: 1.2 }}
+                  >
+                    {opt.desc}
+                  </div>
+                </button>
+              )
+            })}
+          </div>
+        </div>
+
         {/* 开始游戏按钮 */}
-        <Link
-          href="/game"
+        <button
+          onClick={handleStart}
           className="font-pixel text-white rounded-lg transition-all duration-200 cursor-pointer"
           style={{
             backgroundColor: '#F43F5E',
@@ -118,22 +210,23 @@ export default function GameCover() {
             fontSize: '12px',
             letterSpacing: '0.1em',
             boxShadow: '0 0 20px rgba(244, 63, 94, 0.4)',
+            border: 'none',
           }}
           onMouseEnter={e => {
-            const el = e.currentTarget as HTMLAnchorElement
+            const el = e.currentTarget as HTMLButtonElement
             el.style.opacity = '0.9'
             el.style.transform = 'translateY(-2px)'
             el.style.boxShadow = '0 0 30px rgba(244, 63, 94, 0.6)'
           }}
           onMouseLeave={e => {
-            const el = e.currentTarget as HTMLAnchorElement
+            const el = e.currentTarget as HTMLButtonElement
             el.style.opacity = '1'
             el.style.transform = 'translateY(0)'
             el.style.boxShadow = '0 0 20px rgba(244, 63, 94, 0.4)'
           }}
         >
           开始游戏
-        </Link>
+        </button>
 
         {/* 提示文字 */}
         <p