diff --git a/README.md b/README.md
index 5bf2c8c..0e9fe8d 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@
 | 代码块 | Expressive Code（行号、折叠、语言徽章、自定义复制按钮） |
 | 数学公式 | remark-math + KaTeX |
 | 站内搜索 | Pagefind（构建时索引） |
-| 页面切换 | Swup |
+| 页面切换 | Astro View Transitions（`<ClientRouter />`） |
 | 部署 | `./deploy.sh`（rsync 到树莓派 + 云服务器） |
 | 评论系统 | 自托管的 [twikoo](https://twikoo.js.org)（见下） |
 
@@ -60,6 +60,7 @@ src/
 ├── content/        Markdown 内容集合（见下）
 ├── data/           站点配置：站点信息、个人信息、相册、评论、友链
 ├── styles/         全局 CSS
+├── scripts/        浏览器侧交互（lifecycle 契约，见下）
 ├── plugins/        自定义 remark / rehype / Expressive Code 插件
 ├── lib/ hooks/     支撑逻辑
 public/             原样拷贝到产物根目录的静态资源
@@ -68,6 +69,34 @@ public/             原样拷贝到产物根目录的静态资源
 scripts/            内容工具脚本
 ```
 
+## 交互层
+
+除了 React islands，站点还有一批「绑全局监听 / 操作 DOM」的原生脚本（主题切换、
+代码复制、github 卡片、灯箱、移动端菜单、评论、回到顶部）。它们都注册在
+`src/scripts/interactions.ts`，由 `src/layouts/BaseLayout.astro` 引一次。
+
+因为页面切换走 `<ClientRouter />`（Astro View Transitions），DOM 每次导航都会被换掉，
+而**模块脚本只会求值一次**。所以新增交互不要自己监听 `astro:page-load`、也不要用
+`window.__xxxBound` 防重复绑定，改用 `src/scripts/lifecycle.ts`：
+
+```ts
+import { onPage } from "@/scripts/lifecycle"
+
+onPage("my-widget", () => {
+  const el = document.querySelector("[data-my-widget]")
+  if (!el) return                       // 本页没有这个组件：不挂载，也不报错
+  const onClick = () => { /* ... */ }
+  el.addEventListener("click", onClick)
+  return () => el.removeEventListener("click", onClick)   // astro:before-swap 时调用
+})
+```
+
+`lifecycle` 在 `astro:before-swap` 卸载全部、在 `astro:page-load` 挂载全部，
+并保证首屏、切页、模块重复求值这三种情况下都不会重复绑定或漏绑。
+
+页面级的小交互如果**不需要 JS** 就别写 JS：阅读进度条和回到顶部按钮的显隐都由
+CSS 滚动驱动动画（`animation-timeline: scroll()`）负责，脚本只管点击与老浏览器降级。
+
 ## 写作
 
 内容集合定义在 `src/content/config.ts`，共三个：
diff --git a/src/components/ArticleContent.astro b/src/components/ArticleContent.astro
index f227508..f887f0e 100644
--- a/src/components/ArticleContent.astro
+++ b/src/components/ArticleContent.astro
@@ -20,7 +20,7 @@ const primaryTag = tags[0]
 const primaryTagHref = primaryTag ? `/?tag=${encodeURIComponent(primaryTag)}#home-main` : null
 ---
 
-<main class="pt-24 pb-4" data-pagefind-body>
+<main id="main" tabindex="-1" class="pt-24 pb-4" data-pagefind-body>
   <div class="px-6">
     <div class="max-w-[44rem] mx-auto">
     <a
diff --git a/src/components/Comments.astro b/src/components/Comments.astro
index feefbc2..1edb738 100644
--- a/src/components/Comments.astro
+++ b/src/components/Comments.astro
@@ -37,98 +37,6 @@ const isEnabled = Boolean(envId)
             data-lang={commentConfig.lang}
             data-strip-trailing-slash={commentConfig.stripTrailingSlash ? "true" : "false"}
           />
-
-          <script is:inline>
-            ;(() => {
-              const SCRIPT_SRC = "/assets/js/twikoo.min.js"
-
-              /**
-               * 注意：容器是 <div id="twikoo">，而浏览器会把带 id 的元素暴露成
-               * window 上的同名全局变量 —— 所以脚本加载前 window.twikoo 就已经
-               * 是那个 DOM 元素了。这里必须检查真正的 API 是否存在，
-               * 不能只判断 `if (window.twikoo)`，否则会误以为已加载而跳过。
-               */
-              const isLoaded = () =>
-                typeof window.twikoo === "object" && typeof window.twikoo?.init === "function"
-
-              const loadScript = () => {
-                if (isLoaded()) return Promise.resolve()
-
-                const existing = document.querySelector("script[data-twikoo]")
-                if (existing) {
-                  if (existing.dataset.loaded === "true") return Promise.resolve()
-                  return new Promise((resolve, reject) => {
-                    existing.addEventListener("load", () => resolve(), { once: true })
-                    existing.addEventListener(
-                      "error",
-                      () => reject(new Error("twikoo 脚本加载失败")),
-                      { once: true },
-                    )
-                  })
-                }
-
-                return new Promise((resolve, reject) => {
-                  const script = document.createElement("script")
-                  script.src = SCRIPT_SRC
-                  script.async = true
-                  script.dataset.twikoo = "true"
-                  script.onload = () => {
-                    script.dataset.loaded = "true"
-                    resolve()
-                  }
-                  script.onerror = () => reject(new Error("twikoo 脚本加载失败: " + SCRIPT_SRC))
-                  document.head.appendChild(script)
-                })
-              }
-
-              /**
-               * 评论归属路径。本站 trailingSlash 为 "always"，但评论 key 统一去掉
-               * 结尾斜杠（/posts/xxx），与历史数据保持一致。
-               */
-              const getCommentPath = (strip) => {
-                const pathname = window.location.pathname
-                if (strip && pathname.length > 1 && pathname.endsWith("/")) {
-                  return pathname.slice(0, -1)
-                }
-                return pathname
-              }
-
-              const mount = async () => {
-                const container = document.getElementById("twikoo")
-                if (!container) return
-
-                // astro:page-load 在首屏也会触发，用标记避免重复初始化；
-                // 切页时容器是新节点，没有这个标记，所以会正常重新挂载。
-                if (container.dataset.mounted === "true") return
-
-                const envId = container.dataset.envId
-                if (!envId) return
-
-                container.dataset.mounted = "true"
-
-                try {
-                  await loadScript()
-                  await window.twikoo.init({
-                    envId,
-                    el: "#twikoo",
-                    lang: container.dataset.lang || "zh-CN",
-                    path: getCommentPath(container.dataset.stripTrailingSlash === "true"),
-                  })
-                } catch (error) {
-                  // 失败时解除标记，允许下次切页重试
-                  container.dataset.mounted = "false"
-                  console.error("[twikoo] 初始化失败：", error)
-                }
-              }
-
-              if (document.readyState === "loading") {
-                document.addEventListener("DOMContentLoaded", mount)
-              } else {
-                mount()
-              }
-              document.addEventListener("astro:page-load", mount)
-            })()
-          </script>
         </div>
       </div>
     </section>
diff --git a/src/components/ImageLightbox.astro b/src/components/ImageLightbox.astro
index 05a25a2..cdbe744 100644
--- a/src/components/ImageLightbox.astro
+++ b/src/components/ImageLightbox.astro
@@ -8,6 +8,9 @@
  *
  * 用事件委托 + 每次打开时重新收集当前页的图片，所以 ClientRouter 切页后依然有效；
  * 遮罩只在第一次点击时才创建，没点过就不占 DOM。
+ *
+ * 监听器的挂载 / 摘除交给 src/scripts/lifecycle.ts（astro:before-swap 时卸载），
+ * 这里不再需要 `window.__vvLightboxBound` 那套防重复绑定的标记。
  */
 ---
 
@@ -19,6 +22,7 @@
 </style>
 
 <script>
+  import { onPage } from "@/scripts/lifecycle"
   import { openModalFocus } from "@/lib/modal-focus"
 
   const LB_ID = "vv-lightbox"
@@ -107,10 +111,8 @@
     if (overlay) render(overlay)
   }
 
-  if (!(window as unknown as { __vvLightboxBound?: boolean }).__vvLightboxBound) {
-    ;(window as unknown as { __vvLightboxBound?: boolean }).__vvLightboxBound = true
-
-    document.addEventListener("click", (event) => {
+  onPage("lightbox", () => {
+    const handleClick = (event: MouseEvent) => {
       const target = event.target as Element | null
 
       const trigger = target?.closest<HTMLElement>("[data-lightbox-src]")
@@ -130,24 +132,29 @@
       // 点背景关闭（点图片本身不关）
       const overlay = document.getElementById(LB_ID)
       if (overlay && target === overlay) close()
-    })
+    }
 
-    document.addEventListener("keydown", (event) => {
+    const handleKeydown = (event: KeyboardEvent) => {
       const overlay = document.getElementById(LB_ID)
       if (!overlay || overlay.classList.contains("hidden")) return
       if (event.key === "Escape") close()
       if (event.key === "ArrowLeft") step(-1)
       if (event.key === "ArrowRight") step(1)
-    })
+    }
 
-    // 切页时收拾干净，避免残留遮罩锁住滚动
-    document.addEventListener("astro:page-load", () => {
-      // 先还原 inert / 焦点，再移除遮罩，别把上一页的 inert 状态留在新页面上
+    document.addEventListener("click", handleClick)
+    document.addEventListener("keydown", handleKeydown)
+
+    // 切页前收拾干净：还原背景 inert / 焦点、移除遮罩、解开滚动锁。
+    // 这一步现在发生在 astro:before-swap（旧 DOM 还在的时候），比原来挂在
+    // astro:page-load 里补救更早 —— 遮罩不会在新页面上闪一下，也不会残留 inert。
+    return () => {
+      document.removeEventListener("click", handleClick)
+      document.removeEventListener("keydown", handleKeydown)
       releaseFocus?.()
       releaseFocus = null
-      const overlay = document.getElementById(LB_ID)
-      if (overlay) overlay.remove()
+      document.getElementById(LB_ID)?.remove()
       document.body.style.overflow = ""
-    })
-  }
+    }
+  })
 </script>
diff --git a/src/components/bookshelf-content.astro b/src/components/bookshelf-content.astro
index a35c3c1..f8718c4 100644
--- a/src/components/bookshelf-content.astro
+++ b/src/components/bookshelf-content.astro
@@ -106,7 +106,7 @@ const recommendBadge = (status?: string) => {
 <div class="min-h-screen bg-background dark:bg-surface-subtle">
   <SiteHeader />
 
-  <main class="pt-24 pb-24">
+  <main id="main" tabindex="-1" class="pt-24 pb-24">
     <div class="max-w-7xl mx-auto px-4 md:px-8">
       <div class="flex flex-col md:flex-row md:gap-10">
 
diff --git a/src/components/pages/AboutPage.tsx b/src/components/pages/AboutPage.tsx
index 97f86de..8cb0159 100644
--- a/src/components/pages/AboutPage.tsx
+++ b/src/components/pages/AboutPage.tsx
@@ -15,7 +15,7 @@ const journey = [
 export default function AboutPage() {
   return (
     <div className="min-h-screen bg-background dark:bg-surface-subtle">
-      <main className="pt-32 pb-8">
+      <main id="main" tabIndex={-1} className="pt-32 pb-8">
         <div className="max-w-4xl mx-auto px-6">
           {/* Hero Section */}
           <section className="mb-10">
diff --git a/src/components/pages/FriendsPage.astro b/src/components/pages/FriendsPage.astro
index c98cbdc..0575deb 100644
--- a/src/components/pages/FriendsPage.astro
+++ b/src/components/pages/FriendsPage.astro
@@ -52,7 +52,7 @@ const siteInfoText = [
 
 <div class="min-h-screen bg-background dark:bg-surface-subtle overflow-x-hidden">
   <SiteHeader />
-  <main class="pt-24 sm:pt-32 pb-8">
+  <main id="main" tabindex="-1" class="pt-24 sm:pt-32 pb-8">
     <div class="max-w-6xl mx-auto px-6">
       <section class="mb-3">
         <h1 class="text-3xl sm:text-4xl font-bold text-foreground mb-3 flex items-center gap-3">
diff --git a/src/components/site-header.astro b/src/components/site-header.astro
index 24a9d7a..c24852f 100644
--- a/src/components/site-header.astro
+++ b/src/components/site-header.astro
@@ -268,19 +268,23 @@ const isCurrent = (href: string) =>
 </style>
 
 <script>
+  import { onPage } from "@/scripts/lifecycle"
   import { openModalFocus } from "@/lib/modal-focus"
 
-  // Runs on initial page load AND after every Astro View Transition navigation.
-  // DOM nodes are replaced across navigations, so we must rebind listeners each time.
-  const initMobileMenu = () => {
+  /**
+   * 移动端菜单。
+   *
+   * DOM 每次导航都会被换掉，所以「重新绑定」交给 lifecycle：
+   * astro:before-swap 时先按正常流程关一次菜单（还原背景 inert、body 滚动锁、焦点），
+   * 再摘掉监听器；新页面挂载时重新绑一遍。
+   * 原来那套 window.__menuEscBound 标记 + 独立的 astro:before-swap / astro:page-load
+   * 监听器都不再需要。
+   */
+  onPage("mobile-menu", () => {
     const toggle = document.getElementById("mobile-menu-toggle")
     const menu = document.getElementById("mobile-menu")
     if (!toggle || !menu) return
 
-    // Prevent double-binding in case this element is preserved across transitions
-    if (toggle.dataset.menuBound === "1") return
-    toggle.dataset.menuBound = "1"
-
     let prevOverflow = ""
     /** 关闭时用来还原背景 inert 与焦点 */
     let releaseFocus: (() => void) | null = null
@@ -316,47 +320,33 @@ const isCurrent = (href: string) =>
       }
     }
 
-    toggle.addEventListener("click", () => {
-      setOpen(menu.dataset.open !== "true")
-    })
+    const onToggle = () => setOpen(menu.dataset.open !== "true")
 
-    menu.addEventListener("click", (event) => {
+    const onMenuClick = (event: MouseEvent) => {
       const target = event.target as HTMLElement | null
       if (!target) return
-      if (target.closest("[data-dismiss]") || target.closest("a")) {
-        setOpen(false)
-      }
-    })
+      if (target.closest("[data-dismiss]") || target.closest("a")) setOpen(false)
+    }
 
-    // Expose close handler for the module-level Escape listener
-    ;(menu as HTMLElement & { __close?: () => void }).__close = () => setOpen(false)
-  }
-
-  // ESC listener is global; bind only once per full page load.
-  if (!(window as unknown as { __menuEscBound?: boolean }).__menuEscBound) {
-    ;(window as unknown as { __menuEscBound?: boolean }).__menuEscBound = true
-    document.addEventListener("keydown", (event) => {
+    // Esc 只在本页菜单打开时响应；原来是一个「只绑一次」的全局监听器，
+    // 现在随菜单一起挂载 / 卸载，语义更窄也更干净。
+    const onKeydown = (event: KeyboardEvent) => {
       if (event.key !== "Escape") return
-      const menu = document.getElementById("mobile-menu") as
-        | (HTMLElement & { __close?: () => void })
-        | null
-      if (menu?.dataset.open === "true") {
-        event.preventDefault()
-        menu.__close?.()
-      }
-    })
-  }
+      if (menu.dataset.open !== "true") return
+      event.preventDefault()
+      setOpen(false)
+    }
 
-  // Reset body scroll lock on navigation away while menu is open
-  document.addEventListener("astro:before-swap", () => {
-    const menu = document.getElementById("mobile-menu") as
-      | (HTMLElement & { __close?: () => void })
-      | null
-    if (menu?.dataset.open === "true") {
-      // 走 __close 而不是只清 overflow：inert 与焦点也要一起还原
-      menu.__close?.()
+    toggle.addEventListener("click", onToggle)
+    menu.addEventListener("click", onMenuClick)
+    document.addEventListener("keydown", onKeydown)
+
+    return () => {
+      // 菜单开着就切页：先走正常关闭流程还原 inert / 滚动锁 / 焦点，再摘监听器
+      setOpen(false)
+      toggle.removeEventListener("click", onToggle)
+      menu.removeEventListener("click", onMenuClick)
+      document.removeEventListener("keydown", onKeydown)
     }
   })
-
-  document.addEventListener("astro:page-load", initMobileMenu)
 </script>
diff --git a/src/data/reading.json b/src/data/reading.json
index b4df13d..b22ff30 100644
--- a/src/data/reading.json
+++ b/src/data/reading.json
@@ -1,5 +1,5 @@
 {
-  "updatedAt": "2026-09-21T00:13:50.916Z",
+  "updatedAt": "2026-09-21T01:32:16.851Z",
   "source": "weread",
   "books": [
     {
diff --git a/src/layouts/BaseLayout.astro b/src/layouts/BaseLayout.astro
index c366d31..40a7a99 100644
--- a/src/layouts/BaseLayout.astro
+++ b/src/layouts/BaseLayout.astro
@@ -176,28 +176,6 @@ const resolvedTwitterDescription = twitterDescription || description
         window.__applyTheme = applyTheme;
       })();
     </script>
-    <script is:inline>
-      // 主题切换按钮（无水合也可用）
-      (function() {
-        if (window.__themeToggleBound) return;
-        window.__themeToggleBound = true;
-        const toggleTheme = () => {
-          const isDark = document.documentElement.classList.contains('dark');
-          const next = isDark ? 'light' : 'dark';
-          localStorage.setItem('theme', next);
-          document.documentElement.classList.toggle('dark', next === 'dark');
-        };
-        window.__toggleTheme = toggleTheme;
-        document.addEventListener('click', (event) => {
-          const target = event.target;
-          if (!(target instanceof Element)) return;
-          const button = target.closest('[data-theme-toggle]');
-          if (!button) return;
-          event.preventDefault();
-          toggleTheme();
-        });
-      })();
-    </script>
     <script is:inline>
       // 预过滤标记：避免带 tag/category 查询的首页渲染闪动
       (function() {
@@ -214,169 +192,52 @@ const resolvedTwitterDescription = twitterDescription || description
     <ClientRouter />
   </head>
   <body class:list={["bg-background text-foreground", { "font-profile-interface": useHarmonySans }]}>
+    {/*
+      P0-2 跳到正文：键盘/读屏用户的第一个停靠点。样式见 global.css 的 .skip-link，
+      默认用 transform 移出视口（保留在无障碍树里），聚焦时才落回左上角。
+
+      目标锚点 #main 由各页面/内容组件的 <main> 提供；漏加 id 的页面，
+      浏览器的行为是「跳到页面顶部」，不会报错。
+    */}
+    <a href="#main" class="skip-link">跳到正文</a>
+
+    {/*
+      P0-3 阅读进度：完全由 CSS 滚动驱动动画驱动（见 global.css 的 .reading-progress）。
+      不支持 animation-timeline 的浏览器不显示这条线，而不是退化成一条永远满格的横杠。
+    */}
+    <div class="reading-progress" aria-hidden="true">
+      <span class="reading-progress-bar"></span>
+    </div>
+
     <slot />
+
+    {/*
+      P0-3 回到顶部：胶囊形磨砂玻璃。显隐同样默认交给 CSS 滚动驱动动画，
+      这里的 JS 只管点击滚动 + 老浏览器降级（见 src/scripts/back-to-top.ts）。
+    */}
+    <button type="button" class="back-to-top" data-back-to-top>
+      <svg
+        class="back-to-top-icon"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+        stroke-width="1.75"
+        stroke-linecap="round"
+        stroke-linejoin="round"
+        aria-hidden="true"
+      >
+        <path d="M12 19V5M5 12l7-7 7 7"></path>
+      </svg>
+      <span class="back-to-top-text">回到顶部</span>
+    </button>
+
     <ImageLightbox />
-    <script is:inline>
-      // View Transitions 页面切换后重应用主题
-      (function() {
-        const applyTheme = window.__applyTheme
-        if (typeof applyTheme !== "function") return
-        document.addEventListener("astro:page-load", applyTheme)
-        document.addEventListener("astro:after-swap", applyTheme)
-        window.addEventListener("pageshow", applyTheme)
-      })()
-    </script>
-    <script is:inline>
-      // Copy button functionality for Expressive Code
-      function initCopyButtons() {
-        document.querySelectorAll('.expressive-code .copy-btn').forEach(function(btn) {
-          if (btn.dataset.initialized) return;
-          btn.dataset.initialized = 'true';
-          btn.addEventListener('click', async function() {
-            const pre = btn.closest('pre');
-            if (!pre) return;
-            const code = pre.querySelector('code');
-            if (!code) return;
-            // 只提取 .code 元素的内容，排除行号 (.gutter)
-            const lines = code.querySelectorAll('.ec-line .code');
-            const text = Array.from(lines).map(function(line) {
-              return line.textContent || '';
-            }).join('\n');
-            try {
-              await navigator.clipboard.writeText(text);
-              btn.classList.add('copied');
-              setTimeout(function() {
-                btn.classList.remove('copied');
-              }, 2000);
-            } catch (err) {
-              console.error('Failed to copy:', err);
-            }
-          });
-        });
-      }
-      document.addEventListener('DOMContentLoaded', initCopyButtons);
-      document.addEventListener('astro:page-load', initCopyButtons);
-    </script>
-    <script is:inline data-astro-rerun>
-      // GitHub card loader fallback (view transitions safe)
-      (function() {
-        const debugEnabled = () => localStorage.getItem("debugGithubCard") === "1"
-        const debug = (...args) => {
-          if (debugEnabled()) console.log("[GITHUB-CARD]", ...args)
-        }
-        const __gcLangColorsMap = {
-          JavaScript: "#f1e05a",
-          TypeScript: "#3178c6",
-          Python: "#3572A5",
-          Java: "#b07219",
-          "C++": "#f34b7d",
-          C: "#555555",
-          "C#": "#178600",
-          Go: "#00ADD8",
-          Rust: "#dea584",
-          Ruby: "#701516",
-          PHP: "#4F5D95",
-          Swift: "#F05138",
-          Kotlin: "#A97BFF",
-          Dart: "#00B4AB",
-          Scala: "#c22d40",
-          Shell: "#89e051",
-          HTML: "#e34c26",
-          CSS: "#563d7c",
-          SCSS: "#c6538c",
-          Vue: "#41b883",
-          Svelte: "#ff3e00",
-          Astro: "#ff5a03",
-          MDX: "#fcb32c",
-          Markdown: "#083fa1",
-          JSON: "#292929",
-          YAML: "#cb171e",
-          Dockerfile: "#384d54",
-          Makefile: "#427819",
-          Lua: "#000080",
-          Perl: "#0298c3",
-          R: "#198CE7",
-          Julia: "#a270ba",
-          Haskell: "#5e5086",
-          Elixir: "#6e4a7e",
-          Clojure: "#db5855",
-          Objective_C: "#438eff",
-          "Objective-C": "#438eff",
-          Jupyter_Notebook: "#DA5B0B",
-          "Jupyter Notebook": "#DA5B0B",
-          Vim_Script: "#199f4b",
-          TeX: "#3D6117",
-          PowerShell: "#012456",
-        }
 
-        const formatNumber = (value) => {
-          return Intl.NumberFormat("en-us", { notation: "compact", maximumFractionDigits: 1 })
-            .format(value)
-            .replaceAll("\u202f", "")
-        }
-
-        const initGithubCards = (source = "unknown") => {
-          const cards = Array.from(document.querySelectorAll("[data-github-card][data-github-repo]"))
-          debug("init", source, "cards:", cards.length)
-          cards.forEach((card) => {
-            if (!(card instanceof HTMLElement)) return
-            if (card.dataset.githubLoaded === "true") return
-            const repo = card.dataset.githubRepo
-            if (!repo) return
-            card.dataset.githubLoaded = "loading"
-            debug("fetch", repo)
-
-            fetch(`https://api.github.com/repos/${repo}`, { referrerPolicy: "no-referrer" })
-              .then((response) => response.json())
-              .then((data) => {
-                const descEl = card.querySelector(".gc-description")
-                if (descEl) {
-                  descEl.textContent =
-                    data.description?.replace(/:[a-zA-Z0-9_]+:/g, "") || "No description provided"
-                }
-
-                const langEl = card.querySelector(".gc-language")
-                const lang = data.language || ""
-                if (langEl) {
-                  langEl.textContent = lang || "—"
-                  if (lang && __gcLangColorsMap[lang]) {
-                    langEl.style.setProperty("--gc-lang-color", __gcLangColorsMap[lang])
-                  }
-                }
-
-                const forksEl = card.querySelector(".gc-forks")
-                if (forksEl) forksEl.textContent = formatNumber(data.forks || 0)
-
-                const starsEl = card.querySelector(".gc-stars")
-                if (starsEl) starsEl.textContent = formatNumber(data.stargazers_count || 0)
-
-                const licenseEl = card.querySelector(".gc-license")
-                if (licenseEl) licenseEl.textContent = data.license?.spdx_id || "—"
-
-                const avatarEl = card.querySelector(".gc-avatar")
-                if (avatarEl && data.owner?.avatar_url) {
-                  avatarEl.style.backgroundImage = `url(${data.owner.avatar_url})`
-                  avatarEl.style.backgroundColor = "transparent"
-                }
-
-                card.classList.remove("fetch-waiting")
-                card.dataset.githubLoaded = "true"
-                debug("loaded", repo)
-              })
-              .catch(() => {
-                card.classList.add("fetch-error")
-                card.dataset.githubLoaded = "error"
-                debug("error", repo)
-              })
-          })
-        }
-
-        document.addEventListener("DOMContentLoaded", () => initGithubCards("dom"))
-        document.addEventListener("astro:page-load", () => initGithubCards("page-load"))
-        document.addEventListener("astro:after-swap", () => initGithubCards("after-swap"))
-        window.addEventListener("pageshow", () => initGithubCards("pageshow"))
-        window.__initGithubCards = initGithubCards
-      })()
+    <script>
+      // 交互层统一从 lifecycle 挂载 / 卸载（见 src/scripts/lifecycle.ts）。
+      // 原来是四段各自 is:inline、各自用 window.__xxxBound 防重复绑定的脚本；
+      // 现在聚合到一个 module 入口，切页时由 astro:before-swap 统一清理。
+      import "@/scripts/interactions"
     </script>
   </body>
 </html>
diff --git a/src/pages/404.astro b/src/pages/404.astro
index f6be339..fb1a2fc 100644
--- a/src/pages/404.astro
+++ b/src/pages/404.astro
@@ -35,7 +35,7 @@ const entries = [
 <BaseLayout {title} {description} robots="noindex" fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main id="main" class="mx-auto flex min-h-[70vh] max-w-2xl flex-col justify-center px-6 pt-24 pb-20">
+    <main id="main" tabindex="-1" class="mx-auto flex min-h-[70vh] max-w-2xl flex-col justify-center px-6 pt-24 pb-20">
       <p class="mb-4 font-mono text-sm tracking-[0.25em] text-primary">404</p>
 
       <h1 class="mb-4 flex items-center gap-3 text-2xl font-semibold text-foreground sm:text-3xl">
diff --git a/src/pages/[...page].astro b/src/pages/[...page].astro
index 2c7c6a2..f543ee3 100644
--- a/src/pages/[...page].astro
+++ b/src/pages/[...page].astro
@@ -31,7 +31,7 @@ const title =
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-surface-subtle">
     <SiteHeader />
-    <main class="pt-24">
+    <main id="main" tabindex="-1" class="pt-24">
       {/* 同 index.astro：手机端落点贴页眉下沿（列表开头是吸顶胶囊条），lg 以上保留呼吸位 */}
       <section id="home-main" class="scroll-mt-[var(--header-h)] lg:scroll-mt-24">
         <ArticleList
diff --git a/src/pages/gallery/[album].astro b/src/pages/gallery/[album].astro
index 46c265f..91ffdf9 100644
--- a/src/pages/gallery/[album].astro
+++ b/src/pages/gallery/[album].astro
@@ -31,7 +31,7 @@ const description = album.description ?? "相册"
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main class="pt-20 pb-16">
+    <main id="main" tabindex="-1" class="pt-20 pb-16">
       {/* 封面横幅 */}
       <section class="relative w-full overflow-hidden">
         {cover ? (
diff --git a/src/pages/gallery/index.astro b/src/pages/gallery/index.astro
index dc183f1..95ff997 100644
--- a/src/pages/gallery/index.astro
+++ b/src/pages/gallery/index.astro
@@ -15,7 +15,7 @@ const allTags = getAllAlbumTags(albums)
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main class="pt-24 sm:pt-32 pb-16">
+    <main id="main" tabindex="-1" class="pt-24 sm:pt-32 pb-16">
       <div class="max-w-6xl mx-auto px-6">
         {/* 页头 */}
         <section class="mb-8">
diff --git a/src/pages/index.astro b/src/pages/index.astro
index c342ea1..881ac34 100644
--- a/src/pages/index.astro
+++ b/src/pages/index.astro
@@ -21,7 +21,7 @@ const thoughtPreviews = thoughts.map((thought) => toThoughtPreview(thought)).sli
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main>
+    <main id="main" tabindex="-1">
       <Hero client:idle />
       {/*
         手机端锚点落点要贴页眉下沿：这一屏列表的第一个元素是吸顶胶囊条
diff --git a/src/pages/studies/[id].astro b/src/pages/studies/[id].astro
index e605ac6..b80cc89 100644
--- a/src/pages/studies/[id].astro
+++ b/src/pages/studies/[id].astro
@@ -20,7 +20,7 @@ const description = study.epigraph ?? ""
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle" data-pagefind-ignore>
     <SiteHeader />
-    <main class="pt-20">
+    <main id="main" tabindex="-1" class="pt-20">
       <StudyDetailView client:idle study={study} />
     </main>
     <Footer />
diff --git a/src/pages/studies/index.astro b/src/pages/studies/index.astro
index cf9d955..cf05560 100644
--- a/src/pages/studies/index.astro
+++ b/src/pages/studies/index.astro
@@ -15,7 +15,7 @@ const studies = await getAllStudies()
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle" data-pagefind-ignore>
     <SiteHeader />
-    <main class="pt-20">
+    <main id="main" tabindex="-1" class="pt-20">
       <StudiesList client:idle studies={studies} />
     </main>
     <Footer />
diff --git a/src/pages/thoughts/index.astro b/src/pages/thoughts/index.astro
index 9f0e72e..9713d61 100644
--- a/src/pages/thoughts/index.astro
+++ b/src/pages/thoughts/index.astro
@@ -16,7 +16,7 @@ const thoughtsWithContent = allThoughts.map((thought) => toThoughtMeta(thought))
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main class="pt-20">
+    <main id="main" tabindex="-1" class="pt-20">
       <section id="thoughts-main" class="scroll-mt-24">
         <ThoughtsView client:idle thoughts={thoughtsWithContent} />
       </section>
diff --git a/src/pages/timeline/index.astro b/src/pages/timeline/index.astro
index ddc88ed..f545807 100644
--- a/src/pages/timeline/index.astro
+++ b/src/pages/timeline/index.astro
@@ -21,7 +21,7 @@ const timelineItems = posts.map((post) => ({
 <BaseLayout {title} {description} fontProfile="interface">
   <div class="min-h-screen bg-background dark:bg-surface-subtle">
     <SiteHeader />
-    <main class="pt-24">
+    <main id="main" tabindex="-1" class="pt-24">
       <Timeline items={timelineItems} />
     </main>
     <Footer />
diff --git a/src/scripts/back-to-top.ts b/src/scripts/back-to-top.ts
new file mode 100644
index 0000000..1f16da7
--- /dev/null
+++ b/src/scripts/back-to-top.ts
@@ -0,0 +1,59 @@
+import { onPage } from "./lifecycle"
+
+/**
+ * 回到顶部按钮。
+ *
+ * 显隐**默认交给 CSS**：`animation-timeline: scroll(root block)` 让按钮随滚动位置
+ * 淡入，不需要任何 scroll 监听（见 global.css 的 .back-to-top）。
+ * 这里只负责两件事：
+ *   1. 点击后平滑回到顶部；
+ *   2. 给不支持滚动驱动动画的浏览器（Firefox < 144 / Safari < 26）做降级。
+ */
+
+/** 与 global.css 里 animation-range 的起点保持一致 */
+const REVEAL_AFTER_PX = 480
+
+const supportsScrollTimeline = () =>
+  typeof CSS !== "undefined" &&
+  typeof CSS.supports === "function" &&
+  CSS.supports("animation-timeline: scroll()")
+
+onPage("back-to-top", () => {
+  const button = document.querySelector<HTMLElement>("[data-back-to-top]")
+  if (!button) return
+
+  const onClick = () => {
+    const reduceMotion = window.matchMedia("(prefers-reduced-motion: reduce)").matches
+    window.scrollTo({ top: 0, behavior: reduceMotion ? "auto" : "smooth" })
+  }
+  button.addEventListener("click", onClick)
+
+  if (supportsScrollTimeline()) {
+    return () => button.removeEventListener("click", onClick)
+  }
+
+  // ——— 降级路径 ———
+  // rAF 节流，且只在跨越阈值时才写 class：滚动本身不产生布局读取（只用 scrollY）
+  const root = document.documentElement
+  root.classList.add("no-scroll-timeline")
+
+  let frame = 0
+  const update = () => {
+    frame = 0
+    button.classList.toggle("is-visible", window.scrollY > REVEAL_AFTER_PX)
+  }
+  const onScroll = () => {
+    if (frame) return
+    frame = window.requestAnimationFrame(update)
+  }
+
+  window.addEventListener("scroll", onScroll, { passive: true })
+  update()
+
+  return () => {
+    window.removeEventListener("scroll", onScroll)
+    if (frame) window.cancelAnimationFrame(frame)
+    button.removeEventListener("click", onClick)
+    root.classList.remove("no-scroll-timeline")
+  }
+})
diff --git a/src/scripts/comments.ts b/src/scripts/comments.ts
new file mode 100644
index 0000000..c2a4a64
--- /dev/null
+++ b/src/scripts/comments.ts
@@ -0,0 +1,95 @@
+import { onPage } from "./lifecycle"
+
+/**
+ * twikoo 评论区的挂载。
+ *
+ * 原来这段逻辑内联在 Comments.astro 里，靠 `DOMContentLoaded` + `astro:page-load`
+ * 双重触发、再用容器上的 `dataset.mounted` 去重。现在只声明「怎么挂载」，
+ * 节流与清理交给 lifecycle。
+ *
+ * 两个容易踩的坑（来自原来的注释，保留在这里免得以后重蹈）：
+ *
+ * 1. 容器是 `<div id="twikoo">`，浏览器会把带 id 的元素暴露成 `window.twikoo`
+ *    —— 所以脚本加载前 `window.twikoo` **就已经是那个 DOM 元素了**。判断是否
+ *    加载完成必须检查真正的 API（`init` 是不是函数），不能只判断 `if (window.twikoo)`。
+ * 2. twikoo 的基础样式必须由静态 `<link>` 引入（见 Comments.astro）：脚本自己只会
+ *    往 head 里注入一次样式，而 ClientRouter 切页会清掉它不认识的 `<style>`，
+ *    表现为「从一篇带评论的文章点进另一篇后评论区排版全崩」。
+ */
+
+const SCRIPT_SRC = "/assets/js/twikoo.min.js"
+
+type TwikooApi = { init: (options: Record<string, unknown>) => Promise<unknown> }
+
+const twikooApi = (): TwikooApi | null => {
+  const candidate = (window as unknown as { twikoo?: unknown }).twikoo
+  if (candidate && typeof candidate === "object" && typeof (candidate as TwikooApi).init === "function") {
+    return candidate as TwikooApi
+  }
+  return null
+}
+
+const loadScript = () => {
+  if (twikooApi()) return Promise.resolve()
+
+  const existing = document.querySelector<HTMLScriptElement>("script[data-twikoo]")
+  if (existing) {
+    if (existing.dataset.loaded === "true") return Promise.resolve()
+    return new Promise<void>((resolve, reject) => {
+      existing.addEventListener("load", () => resolve(), { once: true })
+      existing.addEventListener("error", () => reject(new Error("twikoo 脚本加载失败")), { once: true })
+    })
+  }
+
+  return new Promise<void>((resolve, reject) => {
+    const script = document.createElement("script")
+    script.src = SCRIPT_SRC
+    script.async = true
+    script.dataset.twikoo = "true"
+    script.onload = () => {
+      script.dataset.loaded = "true"
+      resolve()
+    }
+    script.onerror = () => reject(new Error("twikoo 脚本加载失败: " + SCRIPT_SRC))
+    document.head.appendChild(script)
+  })
+}
+
+/**
+ * 评论归属路径。本站 trailingSlash 为 "always"，但评论 key 统一去掉结尾斜杠
+ * （/posts/xxx），与历史数据保持一致。
+ */
+const getCommentPath = (strip: boolean) => {
+  const { pathname } = window.location
+  if (strip && pathname.length > 1 && pathname.endsWith("/")) return pathname.slice(0, -1)
+  return pathname
+}
+
+onPage("comments", () => {
+  const container = document.getElementById("twikoo")
+  if (!container) return
+
+  const envId = container.dataset.envId
+  if (!envId) return
+
+  // 首屏与 astro:page-load 都可能触发挂载，用容器标记兜住重复初始化
+  if (container.dataset.mounted === "true") return
+  container.dataset.mounted = "true"
+
+  loadScript()
+    .then(() => {
+      // 脚本加载期间用户可能已经切页，容器被摘出文档就别再初始化了
+      if (!container.isConnected) return
+      return twikooApi()?.init({
+        envId,
+        el: "#twikoo",
+        lang: container.dataset.lang || "zh-CN",
+        path: getCommentPath(container.dataset.stripTrailingSlash === "true"),
+      })
+    })
+    .catch((error) => {
+      // 失败时解除标记，下次挂载可以重试
+      container.dataset.mounted = "false"
+      console.error("[twikoo] 初始化失败：", error)
+    })
+})
diff --git a/src/scripts/copy-button.ts b/src/scripts/copy-button.ts
index 554e212..89d19df 100644
--- a/src/scripts/copy-button.ts
+++ b/src/scripts/copy-button.ts
@@ -1,33 +1,44 @@
-// Copy button functionality for Expressive Code
-export function initCopyButtons() {
-  document.querySelectorAll('.expressive-code .copy-btn').forEach((btn) => {
-    btn.addEventListener('click', async () => {
-      const pre = btn.closest('pre');
-      if (!pre) return;
+import { onPage } from "./lifecycle"
 
-      const code = pre.querySelector('code');
-      if (!code) return;
+/**
+ * Expressive Code 代码块的复制按钮。
+ *
+ * 用事件委托而不是逐个按钮绑定：切页后代码块是全新节点，委托挂在 `document` 上
+ * 由 lifecycle 负责摘挂，既不需要 `dataset.initialized` 标记，也不会遗漏
+ * 懒加载进来的代码块。
+ */
 
-      const text = code.textContent || '';
+/** 与 global.css 里 `.copy-btn.copied` 的反馈时长保持一致 */
+const COPIED_FEEDBACK_MS = 2000
 
-      try {
-        await navigator.clipboard.writeText(text);
-        btn.classList.add('copied');
-        setTimeout(() => {
-          btn.classList.remove('copied');
-        }, 2000);
-      } catch (err) {
-        console.error('Failed to copy:', err);
-      }
-    });
-  });
-}
+onPage("copy-buttons", () => {
+  const onClick = async (event: MouseEvent) => {
+    const target = event.target
+    if (!(target instanceof Element)) return
 
-// Auto-initialize on DOM ready
-if (typeof document !== 'undefined') {
-  if (document.readyState === 'loading') {
-    document.addEventListener('DOMContentLoaded', initCopyButtons);
-  } else {
-    initCopyButtons();
+    const button = target.closest<HTMLElement>(".expressive-code .copy-btn")
+    if (!button) return
+
+    const code = button.closest("pre")?.querySelector("code")
+    if (!code) return
+
+    // 只取 .code 的内容：带上 .gutter 的话行号会被一起复制进去
+    const lines = code.querySelectorAll(".ec-line .code")
+    const text = lines.length
+      ? Array.from(lines)
+          .map((line) => line.textContent ?? "")
+          .join("\n")
+      : (code.textContent ?? "")
+
+    try {
+      await navigator.clipboard.writeText(text)
+      button.classList.add("copied")
+      window.setTimeout(() => button.classList.remove("copied"), COPIED_FEEDBACK_MS)
+    } catch (error) {
+      console.error("Failed to copy:", error)
+    }
   }
-}
+
+  document.addEventListener("click", onClick)
+  return () => document.removeEventListener("click", onClick)
+})
diff --git a/src/scripts/github-cards.ts b/src/scripts/github-cards.ts
new file mode 100644
index 0000000..cd7d2fe
--- /dev/null
+++ b/src/scripts/github-cards.ts
@@ -0,0 +1,129 @@
+import { onPage } from "./lifecycle"
+
+/**
+ * GitHub 仓库卡片：把 `[data-github-card][data-github-repo]` 的占位内容换成实时数据。
+ *
+ * 卡片是构建时渲染的静态骨架（见 Markdown 里的 ::github 语法），这里只做「补数据」。
+ * 每张卡片用 `dataset.githubLoaded` 标记进度，所以切页重挂时不会重复请求同一个仓库
+ * —— 这个标记是必要的：lifecycle 每页都会重新调用挂载函数。
+ */
+
+const LANG_COLORS: Record<string, string> = {
+  JavaScript: "#f1e05a",
+  TypeScript: "#3178c6",
+  Python: "#3572A5",
+  Java: "#b07219",
+  "C++": "#f34b7d",
+  C: "#555555",
+  "C#": "#178600",
+  Go: "#00ADD8",
+  Rust: "#dea584",
+  Ruby: "#701516",
+  PHP: "#4F5D95",
+  Swift: "#F05138",
+  Kotlin: "#A97BFF",
+  Dart: "#00B4AB",
+  Scala: "#c22d40",
+  Shell: "#89e051",
+  HTML: "#e34c26",
+  CSS: "#563d7c",
+  SCSS: "#c6538c",
+  Vue: "#41b883",
+  Svelte: "#ff3e00",
+  Astro: "#ff5a03",
+  MDX: "#fcb32c",
+  Markdown: "#083fa1",
+  JSON: "#292929",
+  YAML: "#cb171e",
+  Dockerfile: "#384d54",
+  Makefile: "#427819",
+  Lua: "#000080",
+  Perl: "#0298c3",
+  R: "#198CE7",
+  Julia: "#a270ba",
+  Haskell: "#5e5086",
+  Elixir: "#6e4a7e",
+  Clojure: "#db5855",
+  Objective_C: "#438eff",
+  "Objective-C": "#438eff",
+  Jupyter_Notebook: "#DA5B0B",
+  "Jupyter Notebook": "#DA5B0B",
+  Vim_Script: "#199f4b",
+  TeX: "#3D6117",
+  PowerShell: "#012456",
+}
+
+type GithubRepo = {
+  description?: string
+  language?: string
+  forks?: number
+  stargazers_count?: number
+  license?: { spdx_id?: string }
+  owner?: { avatar_url?: string }
+}
+
+const formatNumber = (value: number) =>
+  Intl.NumberFormat("en-us", { notation: "compact", maximumFractionDigits: 1 })
+    .format(value)
+    .replaceAll("\u202f", "")
+
+const debugEnabled = () => localStorage.getItem("debugGithubCard") === "1"
+const debug = (...args: unknown[]) => {
+  if (debugEnabled()) console.log("[GITHUB-CARD]", ...args)
+}
+
+const initGithubCards = () => {
+  const cards = Array.from(document.querySelectorAll<HTMLElement>("[data-github-card][data-github-repo]"))
+  debug("init cards:", cards.length)
+
+  cards.forEach((card) => {
+    // 已经加载成功 / 正在加载 / 已失败过的卡片都跳过，避免切页重挂时重复请求
+    if (card.dataset.githubLoaded) return
+
+    const repo = card.dataset.githubRepo
+    if (!repo) return
+    card.dataset.githubLoaded = "loading"
+
+    fetch(`https://api.github.com/repos/${repo}`, { referrerPolicy: "no-referrer" })
+      .then((response) => response.json() as Promise<GithubRepo>)
+      .then((data) => {
+        const setText = (selector: string, value: string) => {
+          const el = card.querySelector(selector)
+          if (el) el.textContent = value
+        }
+
+        setText(".gc-description", data.description?.replace(/:[a-zA-Z0-9_]+:/g, "") || "No description provided")
+        setText(".gc-forks", formatNumber(data.forks || 0))
+        setText(".gc-stars", formatNumber(data.stargazers_count || 0))
+        setText(".gc-license", data.license?.spdx_id || "—")
+
+        const language = data.language || ""
+        const langEl = card.querySelector<HTMLElement>(".gc-language")
+        if (langEl) {
+          langEl.textContent = language || "—"
+          if (language && LANG_COLORS[language]) {
+            langEl.style.setProperty("--gc-lang-color", LANG_COLORS[language])
+          }
+        }
+
+        const avatarEl = card.querySelector<HTMLElement>(".gc-avatar")
+        if (avatarEl && data.owner?.avatar_url) {
+          avatarEl.style.backgroundImage = `url(${data.owner.avatar_url})`
+          avatarEl.style.backgroundColor = "transparent"
+        }
+
+        card.classList.remove("fetch-waiting")
+        card.dataset.githubLoaded = "true"
+        debug("loaded", repo)
+      })
+      .catch(() => {
+        card.classList.add("fetch-error")
+        card.dataset.githubLoaded = "error"
+        debug("error", repo)
+      })
+  })
+}
+
+onPage("github-cards", () => {
+  initGithubCards()
+})
diff --git a/src/scripts/interactions.ts b/src/scripts/interactions.ts
new file mode 100644
index 0000000..8c88c4c
--- /dev/null
+++ b/src/scripts/interactions.ts
@@ -0,0 +1,16 @@
+/**
+ * 交互层入口。
+ *
+ * 全站的「绑定全局监听 / 操作 DOM」类脚本都在这里汇总，由 BaseLayout 引一次。
+ * 每个模块自己负责 `onPage(key, mount)` 注册，并返回卸载函数 —— 见 lifecycle.ts。
+ *
+ * 注意这里**不要**写 `import "..."` 之外的逻辑：入口只做聚合，任何一段交互出问题
+ * 都应该能单独从这个列表里摘掉，而不影响其他交互。
+ */
+
+import "./theme"
+import "./copy-button"
+import "./github-cards"
+import "./back-to-top"
+// 评论区：只有页面上真的存在 #twikoo 时才会做事，twikoo 库本身仍是按需拉取
+import "./comments"
diff --git a/src/scripts/lifecycle.ts b/src/scripts/lifecycle.ts
new file mode 100644
index 0000000..030be0b
--- /dev/null
+++ b/src/scripts/lifecycle.ts
@@ -0,0 +1,126 @@
+/**
+ * 页面生命周期注册表 —— 所有需要「绑定全局监听 / 操作 DOM」的脚本都从这里挂载。
+ *
+ * ## 为什么要有这个文件
+ *
+ * 本站用 Astro 的 ClientRouter 做切页，DOM 每次导航都会被换掉，但**模块脚本只会
+ * 求值一次**。于是每加一个交互，就得自己回答三个问题：什么时候挂载、切页时怎么
+ * 清理、怎么防止重复绑定。原来的答案是「各自监听 astro:page-load + 一个
+ * `window.__xxxBound` 全局布尔量」，结果是：
+ *
+ *   - 绑在 `document` 上的监听器**永远不会被摘掉**，只在 `astro:page-load` 里
+ *     再加一层。旧闭包捕获的元素早就从 DOM 里消失了，却还在每次点击/按键时跑一遍；
+ *   - 没有任何地方负责卸载。弹层开着就切页时，背景的 `inert`、`body` 的
+ *     `overflow: hidden`、遮罩节点都可能残留到新页面上。
+ *
+ * 现在每个交互只声明「怎么挂载」，顺带返回「怎么卸载」：
+ *
+ * ```ts
+ * import { onPage } from "@/scripts/lifecycle"
+ *
+ * onPage("my-widget", () => {
+ *   const el = document.querySelector("[data-my-widget]")
+ *   if (!el) return                       // 本页没有这个组件：不挂载，也不报错
+ *   const onClick = () => { ... }
+ *   el.addEventListener("click", onClick)
+ *   return () => el.removeEventListener("click", onClick)   // 切页前调用
+ * })
+ * ```
+ *
+ * ## 时序
+ *
+ * - `astro:before-swap`：先卸载**全部**已挂载项（此时旧 DOM 还在，弹层能正常还原
+ *   焦点与 inert），然后清空挂载状态；
+ * - 新页面的脚本在 swap 过程中求值并注册；
+ * - `astro:page-load`：挂载全部。
+ *
+ * 注册表本身**不清空**，因为不能保证模块脚本每次切页都会重新求值：某个组件只在
+ * 第一页出现过、之后靠注册表里的旧条目继续在后续页面挂载，是刻意留的行为
+ * （挂载函数自己负责在元素不存在时直接返回）。同名 key 重复注册会覆盖旧条目，
+ * 因此脚本万一真的重新求值也不会累积。
+ */
+
+type Teardown = () => void
+type Mount = () => void | Teardown
+
+const registry = new Map<string, Mount>()
+const teardowns = new Map<string, Teardown>()
+const mounted = new Set<string>()
+
+let autoKey = 0
+/** 当前这一页是否已经跑过挂载阶段，用来接住「注册得比 astro:page-load 还晚」的脚本 */
+let pageMounted = false
+
+const runTeardown = (key: string) => {
+  const off = teardowns.get(key)
+  teardowns.delete(key)
+  if (!off) return
+  try {
+    off()
+  } catch (error) {
+    // 卸载出错不能连累其他脚本，否则残留的 inert / overflow 就再也清不掉了
+    console.error(`[lifecycle] "${key}" 卸载失败：`, error)
+  }
+}
+
+const mountOne = (key: string) => {
+  if (mounted.has(key)) return
+  const mount = registry.get(key)
+  if (!mount) return
+
+  mounted.add(key)
+  try {
+    const off = mount()
+    if (typeof off === "function") teardowns.set(key, off)
+  } catch (error) {
+    // 同理：一个脚本挂载失败不该拖垮同页面的其他交互
+    console.error(`[lifecycle] "${key}" 挂载失败：`, error)
+  }
+}
+
+const mountAll = () => {
+  pageMounted = true
+  for (const key of registry.keys()) mountOne(key)
+}
+
+const unmountAll = () => {
+  pageMounted = false
+  for (const key of Array.from(teardowns.keys())) runTeardown(key)
+  mounted.clear()
+}
+
+/**
+ * 注册一个交互。
+ *
+ * @param key    稳定且唯一的名字。重复注册会覆盖上一条（而不是叠加）。
+ * @param mount  挂载函数；返回的函数会在切页前被调用，用来卸载。
+ */
+export function onPage(key: string, mount: Mount): void
+export function onPage(mount: Mount): void
+export function onPage(keyOrMount: string | Mount, maybeMount?: Mount): void {
+  const key = typeof keyOrMount === "string" ? keyOrMount : `__auto:${autoKey++}`
+  const mount = typeof keyOrMount === "string" ? maybeMount : keyOrMount
+  if (typeof mount !== "function") {
+    throw new TypeError(`[lifecycle] "${key}" 缺少挂载函数`)
+  }
+
+  // 覆盖注册：先卸旧的，避免同一页面里新旧两份监听器并存
+  if (mounted.has(key)) {
+    runTeardown(key)
+    mounted.delete(key)
+  }
+
+  registry.set(key, mount)
+  if (pageMounted) mountOne(key)
+}
+
+document.addEventListener("astro:before-swap", unmountAll)
+document.addEventListener("astro:page-load", mountAll)
+
+// 首屏：处理过的 <script> 是 module，求值时 DOM 已经解析完，直接挂载即可；
+// 另外 astro:page-load 在首屏也会触发，靠 mounted 集合保证不会挂第二遍。
+if (document.readyState === "loading") {
+  document.addEventListener("DOMContentLoaded", mountAll, { once: true })
+} else {
+  mountAll()
+}
diff --git a/src/scripts/theme.ts b/src/scripts/theme.ts
new file mode 100644
index 0000000..50ac62d
--- /dev/null
+++ b/src/scripts/theme.ts
@@ -0,0 +1,38 @@
+import { onPage } from "./lifecycle"
+
+/**
+ * 主题切换。
+ *
+ * 「防止刷新闪白」的那段内联脚本留在 BaseLayout 的 `<head>` 里（必须在首次绘制前
+ * 同步执行，不能变成 module），这里只负责点击委托，以及切页后重新应用主题。
+ */
+
+const head = () => window as unknown as { __applyTheme?: () => void }
+
+/** 切页后 `<html>` 不一定保留着上一页的 class，重新按 localStorage / 系统偏好落一次 */
+const applyTheme = () => head().__applyTheme?.()
+
+onPage("theme-toggle", () => {
+  const onClick = (event: MouseEvent) => {
+    const target = event.target
+    if (!(target instanceof Element)) return
+    if (!target.closest("[data-theme-toggle]")) return
+
+    event.preventDefault()
+    const next = document.documentElement.classList.contains("dark") ? "light" : "dark"
+    try {
+      localStorage.setItem("theme", next)
+    } catch {
+      // 隐私模式下 localStorage 可能直接抛异常；主题仍然应该切过去
+    }
+    document.documentElement.classList.toggle("dark", next === "dark")
+  }
+
+  document.addEventListener("click", onClick)
+  applyTheme()
+
+  return () => document.removeEventListener("click", onClick)
+})
+
+// bfcache 恢复不走 ClientRouter，不会触发 astro:page-load，得单独兜一次
+window.addEventListener("pageshow", applyTheme)
diff --git a/src/styles/global.css b/src/styles/global.css
index 9b333ba..f420d71 100644
--- a/src/styles/global.css
+++ b/src/styles/global.css
@@ -1069,3 +1069,206 @@ a.card-github:hover .github-logo {
 .thoughts-timeline-body li + li { margin-top: 4px; }
 .thoughts-timeline-body li > ul,
 .thoughts-timeline-body li > ol { margin: 4px 0; }
+
+/* ============================================================================
+ * 交互层：跳到正文 / 阅读进度 / 回到顶部
+ *
+ * 这一节的三样东西都属于「P0 基础交互」，共同点是**尽量不依赖 JS**：
+ * 前两个完全由 CSS 负责，回到顶部只在老浏览器上才走降级脚本。
+ * ========================================================================== */
+
+/* ——— 跳到正文 ———
+ * 默认用 transform 移出视口而不是 display:none / visibility:hidden：
+ * 后者会同时把它从无障碍树和 Tab 顺序里摘掉，那这个链接就永远按不到了。
+ * 用 translate 只是把它画到屏幕外，键盘仍然能聚焦（WCAG 2.4.1 跳过重复区块）。
+ */
+.skip-link {
+  position: fixed;
+  top: 0.75rem;
+  left: 0.75rem;
+  z-index: 200;
+  padding: 0.5rem 0.875rem;
+  border: 1px solid var(--border);
+  border-radius: 9999px;
+  background-color: var(--card);
+  color: var(--foreground);
+  font-size: 0.8125rem;
+  font-weight: 500;
+  line-height: 1;
+  box-shadow: 0 10px 30px -12px oklch(0 0 0 / 0.35);
+  transform: translateY(calc(-100% - 1rem));
+  transition: transform 160ms cubic-bezier(0.22, 1, 0.36, 1);
+}
+.skip-link:focus-visible,
+.skip-link:focus {
+  transform: none;
+  outline: 2px solid color-mix(in oklch, var(--primary) 45%, transparent);
+  outline-offset: 2px;
+}
+@media (prefers-reduced-motion: reduce) {
+  .skip-link { transition-duration: 1ms; }
+}
+
+/* ——— 阅读进度条 ———
+ * 位置：视口最顶端 2px。z-index 55 夹在页眉（50）和移动端菜单（60）之间，
+ * 所以它会压在页眉上边缘，但打开菜单 / 灯箱时会被正确遮住。
+ *
+ * 用滚动驱动动画（animation-timeline: scroll()）而不是 scroll 事件：
+ * 不占主线程、不产生强制同步布局，而且**文档不可滚动时时间线是 inactive**，
+ * 进度条自然停在 scaleX(0) —— 短页面不会出现一条莫名其妙的满格横杠。
+ * 不支持的浏览器（Firefox < 144）就整条不显示，不做 JS 兜底：
+ * 它只是锦上添花的信息，不值得为此常驻一个 scroll 监听。
+ */
+.reading-progress {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  z-index: 55;
+  height: 2px;
+  pointer-events: none;
+}
+.reading-progress-bar {
+  display: block;
+  height: 100%;
+  background-color: var(--primary);
+  transform: scaleX(0);
+  transform-origin: 0 50%;
+}
+@keyframes reading-progress-grow {
+  from { transform: scaleX(0); }
+  to { transform: scaleX(1); }
+}
+@supports (animation-timeline: scroll()) {
+  .reading-progress-bar {
+    animation: reading-progress-grow linear both;
+    animation-timeline: scroll(root block);
+  }
+}
+
+/* ——— 回到顶部 ———
+ * 胶囊形磨砂玻璃。
+ *
+ * 关于 backdrop-filter 的成本：页眉在 2026-09-20 主动去掉了模糊（iPad Air 4 上
+ * 全幅宽 24px 模糊每帧重算，滚动掉帧）。这里仍然用模糊，理由是**面积**：
+ * 这个按钮约 40×110 CSS px，不到页眉的 1/50，模糊半径也从 24px 降到 10px。
+ * 如果哪天真在低端设备上观察到掉帧，第一个该降级的就是它（见下面的
+ * prefers-reduced-transparency 分支，改成实色即可）。
+ *
+ * 显隐默认由滚动驱动动画负责（不需要 scroll 监听）；只有不支持
+ * animation-timeline 的浏览器才会由 back-to-top.ts 加 .is-visible 走降级路径。
+ */
+.back-to-top {
+  position: fixed;
+  right: max(1.25rem, env(safe-area-inset-right, 0px));
+  bottom: max(1.25rem, env(safe-area-inset-bottom, 0px));
+  z-index: 55;
+
+  display: inline-flex;
+  align-items: center;
+  gap: 0.375rem;
+  height: 2.5rem;
+  padding-inline: 0.875rem;
+
+  border: 1px solid color-mix(in oklch, var(--border) 80%, transparent);
+  border-radius: 9999px;
+  /* 兜底：不支持 backdrop-filter 时用实色，保证文字对比度 */
+  background-color: var(--card);
+  color: var(--content-secondary);
+  font-size: 0.8125rem;
+  font-weight: 500;
+  line-height: 1;
+  letter-spacing: 0.01em;
+  box-shadow: 0 10px 28px -14px oklch(0 0 0 / 0.4);
+  cursor: pointer;
+
+  opacity: 0;
+  visibility: hidden;
+  transform: translateY(10px) scale(0.96);
+  transition:
+    opacity 200ms ease,
+    transform 260ms cubic-bezier(0.22, 1, 0.36, 1),
+    /* 隐藏时把 visibility 推迟到淡出结束，避免按钮在半透明状态就失去交互 */
+    visibility 0s linear 200ms,
+    color 160ms ease,
+    background-color 160ms ease,
+    border-color 160ms ease;
+}
+.back-to-top:hover {
+  color: var(--foreground);
+  border-color: color-mix(in oklch, var(--primary) 35%, var(--border));
+}
+.back-to-top:active {
+  /* 位移动画在支持滚动时间线的浏览器里会被动画覆盖，所以按压反馈主要靠底色 */
+  transform: translateY(1px) scale(0.985);
+  background-color: color-mix(in oklch, var(--card) 82%, transparent);
+}
+.back-to-top:focus-visible {
+  outline: 2px solid color-mix(in oklch, var(--primary) 45%, transparent);
+  outline-offset: 2px;
+}
+.back-to-top-icon {
+  width: 1rem;
+  height: 1rem;
+  flex: none;
+}
+.back-to-top-text {
+  white-space: nowrap;
+}
+
+@supports ((backdrop-filter: blur(10px)) or (-webkit-backdrop-filter: blur(10px))) {
+  .back-to-top {
+    background-color: color-mix(in oklch, var(--card) 58%, transparent);
+    -webkit-backdrop-filter: blur(10px) saturate(160%);
+    backdrop-filter: blur(10px) saturate(160%);
+  }
+}
+
+@supports (animation-timeline: scroll()) {
+  .back-to-top {
+    /* 显隐交给滚动时间线，这里只留下颜色类过渡 */
+    transition: color 160ms ease, background-color 160ms ease, border-color 160ms ease;
+    animation: back-to-top-reveal linear both;
+    animation-timeline: scroll(root block);
+    /* 滚过 320px 开始淡入，620px 完全就位（与 back-to-top.ts 的 480px 阈值呼应） */
+    animation-range: 320px 620px;
+  }
+}
+@keyframes back-to-top-reveal {
+  from {
+    opacity: 0;
+    visibility: hidden;
+    transform: translateY(10px) scale(0.96);
+  }
+  to {
+    opacity: 1;
+    visibility: visible;
+    transform: none;
+  }
+}
+
+/* 降级路径：只有 back-to-top.ts 判定不支持滚动时间线时才会加上这个 class */
+.no-scroll-timeline .back-to-top.is-visible {
+  opacity: 1;
+  visibility: visible;
+  transform: none;
+}
+
+/* 系统级「降低透明度」：改用实色，别在磨砂上再叠一层看不清的文字 */
+@media (prefers-reduced-transparency: reduce) {
+  .back-to-top {
+    background-color: var(--card);
+    -webkit-backdrop-filter: none;
+    backdrop-filter: none;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .back-to-top {
+    transition-duration: 1ms;
+  }
+  /* 滚动驱动动画不产生自主运动，进度条保留；按钮的位移动画去掉 */
+  .back-to-top:active {
+    transform: none;
+  }
+}