diff --git a/assets/css/style.css b/assets/css/style.css
index 79bef7e..b94bbd2 100644
--- a/assets/css/style.css
+++ b/assets/css/style.css
@@ -136,6 +136,57 @@ nav a {
     box-sizing: border-box;
 }
 
+.portal-nav__menu-toggle {
+    display: none;
+    flex-shrink: 0;
+    margin-left: auto;
+    padding: 10px 12px;
+    border: 0;
+    border-radius: 10px;
+    background: transparent;
+    cursor: pointer;
+    color: var(--primary);
+}
+
+.portal-nav__menu-toggle:focus-visible {
+    outline: 2px solid var(--primary);
+    outline-offset: 3px;
+}
+
+.portal-nav__menu-toggle-icon {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    width: 24px;
+    height: 18px;
+}
+
+.portal-nav__menu-toggle-bar {
+    display: block;
+    width: 22px;
+    height: 2px;
+    border-radius: 1px;
+    background: currentColor;
+    transition: transform 0.2s ease, opacity 0.2s ease;
+}
+
+.portal-nav__menu-toggle-bar+.portal-nav__menu-toggle-bar {
+    margin-top: 5px;
+}
+
+.portal-nav.portal-nav--open .portal-nav__menu-toggle-bar:nth-child(1) {
+    transform: translateY(7px) rotate(45deg);
+}
+
+.portal-nav.portal-nav--open .portal-nav__menu-toggle-bar:nth-child(2) {
+    opacity: 0;
+}
+
+.portal-nav.portal-nav--open .portal-nav__menu-toggle-bar:nth-child(3) {
+    transform: translateY(-7px) rotate(-45deg);
+}
+
 .portal-nav>ul {
     display: flex;
     flex-wrap: wrap;
@@ -205,7 +256,7 @@ nav a {
     color: #3a300a;
 }
 
-/* 淪陷瞬間 · 全員發瘋：第一層向下；第二／三層向右飛出（僅 ≤767px 直向堆疊，避免 1024 平板也壓成直排） */
+/* 淪陷瞬間 · 全員發瘋：第一層向下；第二／三層向右飛出（≥992px）；≤991px 漢堡＋直向堆疊 */
 .portal-nav .portal-submenu .portal-nav__subgroup {
     position: relative;
     z-index: 0;
@@ -349,7 +400,7 @@ nav a {
     display: flex;
 }
 
-@media (min-width: 768px) {
+@media (min-width: 992px) {
 
     .portal-nav .portal-nav__subgroup>.portal-submenu-nested {
         position: absolute !important;
@@ -396,7 +447,63 @@ nav a {
     }
 }
 
-@media (max-width: 767px) {
+@media (max-width: 991px) {
+
+    .portal-nav__menu-toggle {
+        display: inline-flex;
+        align-items: center;
+        justify-content: center;
+    }
+
+    .portal-nav>ul {
+        display: none;
+        flex: 1 1 100%;
+        flex-direction: column;
+        align-items: stretch;
+        justify-content: flex-start;
+        gap: 0;
+        width: 100%;
+        margin-top: 4px;
+        padding: 8px 0 12px;
+        border-top: 1px solid rgba(255, 204, 0, 0.2);
+    }
+
+    .portal-nav.portal-nav--open>ul {
+        display: flex;
+    }
+
+    .portal-nav>ul>li {
+        width: 100%;
+        position: relative;
+    }
+
+    .portal-nav>ul>li>a {
+        justify-content: flex-start;
+        width: 100%;
+        min-height: 44px;
+        padding: 10px 8px;
+        box-sizing: border-box;
+    }
+
+    .portal-nav>ul>li:hover>.portal-submenu,
+    .portal-nav>ul>li:focus-within>.portal-submenu {
+        display: none;
+    }
+
+    .portal-nav>ul>li.open>.portal-submenu {
+        display: grid;
+    }
+
+    .portal-nav .portal-submenu {
+        position: static;
+        width: 100%;
+        min-width: 0;
+        margin-top: 4px;
+        padding: 6px 8px 10px;
+        box-shadow: none;
+        border-radius: 10px;
+        background: rgba(255, 255, 255, 0.06);
+    }
 
     .portal-nav .portal-submenu .portal-nav__subgroup-head::after,
     .portal-nav .portal-nav__subgroup-head--nested::after {
@@ -422,9 +529,17 @@ nav a {
 
     .portal-nav .portal-nav__subgroup:hover>.portal-submenu-nested,
     .portal-nav .portal-nav__subgroup:focus-within>.portal-submenu-nested {
+        display: none;
+    }
+
+    .portal-nav .portal-nav__subgroup.open>.portal-submenu-nested {
         display: flex;
     }
 
+    .portal-nav .portal-submenu .portal-nav__subgroup-head {
+        cursor: pointer;
+    }
+
     .portal-nav .portal-submenu-nested--tier3,
     .portal-nav .portal-nav__subgroup--nested:hover>.portal-submenu-nested--tier3,
     .portal-nav .portal-nav__subgroup--nested:focus-within>.portal-submenu-nested--tier3 {
@@ -444,6 +559,10 @@ nav a {
 
     .portal-nav .portal-nav__subgroup--nested:hover>.portal-submenu-nested--tier3,
     .portal-nav .portal-nav__subgroup--nested:focus-within>.portal-submenu-nested--tier3 {
+        display: none;
+    }
+
+    .portal-nav .portal-nav__subgroup--nested.open>.portal-submenu-nested--tier3 {
         display: flex;
     }
 }
@@ -1566,7 +1685,7 @@ footer a .mark_b {
     padding-right: 10px;
 }
 
-@media (min-width: 768px) {
+@media (min-width: 992px) {
 
     .map-page .portal-nav .portal-submenu .portal-nav__subgroup-head::after {
         right: auto;
@@ -1597,7 +1716,18 @@ footer a .mark_b {
     }
 }
 
-@media (max-width: 767px) {
+@media (max-width: 991px) {
+
+    .map-page .portal-nav>ul>li>a {
+        justify-content: flex-end;
+        text-align: right;
+    }
+
+    .map-page .portal-nav .portal-submenu a,
+    .map-page .portal-nav .portal-submenu .portal-nav__subgroup-head {
+        text-align: right;
+        justify-content: flex-end;
+    }
 
     .map-page .portal-nav .portal-nav__subgroup>.portal-submenu-nested,
     .map-page .portal-nav .portal-nav__subgroup:hover>.portal-submenu-nested,
diff --git a/assets/css/tablet.css b/assets/css/tablet.css
index 4211d79..21286fc 100644
--- a/assets/css/tablet.css
+++ b/assets/css/tablet.css
@@ -1,5 +1,20 @@
 /* iPad／平板 RWD — max-width ≤1180px（含 iPad 直／橫與小平板／小筆電） */
 
+/* 頂欄漢堡：與 style.css 992 斷點一致，避免本檔 1180 規則把選單列壓回橫排 */
+@media (max-width: 991px) {
+
+    .portal-nav>ul {
+        flex: 1 1 100%;
+        flex-wrap: nowrap;
+        justify-content: flex-start;
+        align-items: stretch;
+    }
+
+    .portal-nav>ul>li>a {
+        flex-direction: row;
+    }
+}
+
 @media (max-width: 1180px) {
 
     html:has(.portal-nav) {
@@ -45,7 +60,7 @@
         justify-content: center;
     }
 
-    nav ul {
+    nav:not(.portal-nav):not(.bilivideo-episode-nav) ul {
         gap: clamp(12px, 2vw, 20px);
     }
 
diff --git a/assets/js/portal-nav.js b/assets/js/portal-nav.js
index 1e497df..09821ae 100644
--- a/assets/js/portal-nav.js
+++ b/assets/js/portal-nav.js
@@ -22,6 +22,27 @@
     /** 主選單欄 `mouseleave` 後延遲關閉（ms），方便移入子選單或右側飛出層，避免略偏就關閉 */
     const SUBMENU_CLOSE_DELAY_MS = 650;
 
+    /** 橫向＋右側飛出子選單；≤991px 改漢堡＋直向展開（對齊常見 992 斷點） */
+    const PORTAL_NAV_DESKTOP_MIN_PX = 992;
+
+    function isPortalNavDesktop() {
+        return window.matchMedia(`(min-width: ${PORTAL_NAV_DESKTOP_MIN_PX}px)`).matches;
+    }
+
+    function setPortalNavMenuOpen(nav, open) {
+        nav.classList.toggle("portal-nav--open", open);
+        const toggle = nav.querySelector(".portal-nav__menu-toggle");
+        if (toggle) {
+            toggle.setAttribute("aria-expanded", open ? "true" : "false");
+            toggle.setAttribute("aria-label", open ? "關閉選單" : "開啟選單");
+        }
+        if (!open) {
+            nav.querySelectorAll(":scope > ul > li.open, .portal-nav__subgroup.open").forEach((el) => {
+                el.classList.remove("open");
+            });
+        }
+    }
+
     function pickSoonPhrase() {
         return NAV_SOON_PHRASES[Math.floor(Math.random() * NAV_SOON_PHRASES.length)];
     }
@@ -212,7 +233,14 @@
     function buildPortalNavInnerHTML(rp) {
         return `
 <a class="logo" target="_blank" rel="noopener noreferrer" href="${rp}index.html"><img src="${rp}assets/images/logov.svg" alt="SECHSKIES Logo"></a>
-<ul>
+<button type="button" class="portal-nav__menu-toggle" aria-expanded="false" aria-controls="portal-primary-menu" aria-label="開啟選單">
+    <span class="portal-nav__menu-toggle-icon" aria-hidden="true">
+        <span class="portal-nav__menu-toggle-bar"></span>
+        <span class="portal-nav__menu-toggle-bar"></span>
+        <span class="portal-nav__menu-toggle-bar"></span>
+    </span>
+</button>
+<ul id="portal-primary-menu">
     <li><a target="_blank" rel="noopener noreferrer" href="${rp}index.html"><span class="portal-nav__label">淪陷瞬間</span></a>
         <ul class="portal-submenu">
             <li class="portal-nav__subgroup">
@@ -280,6 +308,49 @@
     navs.forEach((nav) => {
         /* 僅頂層主欄；子選單內巢狀 li 不綁 open，否則會關閉整欄下拉 */
         const items = Array.from(nav.querySelectorAll(":scope > ul > li"));
+        const menuToggle = nav.querySelector(".portal-nav__menu-toggle");
+        const desktopMq = window.matchMedia(`(min-width: ${PORTAL_NAV_DESKTOP_MIN_PX}px)`);
+
+        if (menuToggle) {
+            menuToggle.addEventListener("click", () => {
+                setPortalNavMenuOpen(nav, !nav.classList.contains("portal-nav--open"));
+            });
+        }
+
+        const closeIfOutside = (event) => {
+            if (!nav.contains(event.target)) {
+                setPortalNavMenuOpen(nav, false);
+                items.forEach((item) => item.classList.remove("open"));
+            }
+        };
+
+        document.addEventListener("click", closeIfOutside);
+
+        document.addEventListener("keydown", (event) => {
+            if (event.key === "Escape") setPortalNavMenuOpen(nav, false);
+        });
+
+        desktopMq.addEventListener("change", (event) => {
+            if (event.matches) setPortalNavMenuOpen(nav, false);
+        });
+
+        nav.addEventListener("click", (event) => {
+            if (isPortalNavDesktop()) return;
+
+            const subgroupHead = event.target.closest(".portal-nav__subgroup-head");
+            if (subgroupHead) {
+                event.preventDefault();
+                const subgroup = subgroupHead.closest(".portal-nav__subgroup");
+                if (subgroup) subgroup.classList.toggle("open");
+                return;
+            }
+
+            const link = event.target.closest("a[href]");
+            if (!link || link.classList.contains("logo")) return;
+            if (link.getAttribute("data-coming-soon") === "true") return;
+            const href = link.getAttribute("href");
+            if (href && href !== "#") setPortalNavMenuOpen(nav, false);
+        });
 
         items.forEach((item) => {
             const trigger = item.querySelector(":scope > a");
@@ -287,8 +358,11 @@
             if (!trigger || !submenu) return;
 
             let closeTimer = null;
+            const nestedPanels = Array.from(item.querySelectorAll(".portal-submenu-nested"));
+            const hoverBound = { on: false };
 
             const openItem = () => {
+                if (!isPortalNavDesktop()) return;
                 if (closeTimer) window.clearTimeout(closeTimer);
                 items.forEach((other) => {
                     if (other !== item) other.classList.remove("open");
@@ -314,20 +388,49 @@
                 scheduleClose();
             };
 
-            item.addEventListener("mouseenter", openItem);
-            item.addEventListener("mouseleave", leaveUnlessStillInside);
-            submenu.addEventListener("mouseenter", cancelClose);
-            submenu.addEventListener("mouseleave", leaveUnlessStillInside);
-            item.querySelectorAll(".portal-submenu-nested").forEach((panel) => {
-                panel.addEventListener("mouseenter", cancelClose);
-                panel.addEventListener("mouseleave", leaveUnlessStillInside);
+            const bindDesktopHover = () => {
+                if (hoverBound.on) return;
+                item.addEventListener("mouseenter", openItem);
+                item.addEventListener("mouseleave", leaveUnlessStillInside);
+                submenu.addEventListener("mouseenter", cancelClose);
+                submenu.addEventListener("mouseleave", leaveUnlessStillInside);
+                nestedPanels.forEach((panel) => {
+                    panel.addEventListener("mouseenter", cancelClose);
+                    panel.addEventListener("mouseleave", leaveUnlessStillInside);
+                });
+                hoverBound.on = true;
+            };
+
+            const unbindDesktopHover = () => {
+                if (!hoverBound.on) return;
+                item.removeEventListener("mouseenter", openItem);
+                item.removeEventListener("mouseleave", leaveUnlessStillInside);
+                submenu.removeEventListener("mouseenter", cancelClose);
+                submenu.removeEventListener("mouseleave", leaveUnlessStillInside);
+                nestedPanels.forEach((panel) => {
+                    panel.removeEventListener("mouseenter", cancelClose);
+                    panel.removeEventListener("mouseleave", leaveUnlessStillInside);
+                });
+                hoverBound.on = false;
+                item.classList.remove("open");
+            };
+
+            const syncDesktopHover = () => {
+                if (isPortalNavDesktop()) bindDesktopHover();
+                else unbindDesktopHover();
+            };
+
+            syncDesktopHover();
+            desktopMq.addEventListener("change", syncDesktopHover);
+
+            trigger.addEventListener("focus", () => {
+                if (isPortalNavDesktop()) openItem();
             });
-            trigger.addEventListener("focus", openItem);
 
             trigger.addEventListener("click", (event) => {
                 const isSoon = trigger.getAttribute("data-coming-soon") === "true";
 
-                if (window.innerWidth <= 767) {
+                if (!isPortalNavDesktop()) {
                     event.preventDefault();
                     if (!isSoon && !item.classList.contains("coming-soon")) {
                         item.classList.toggle("open");
@@ -341,12 +444,6 @@
             });
         });
 
-        document.addEventListener("click", (event) => {
-            if (!nav.contains(event.target)) {
-                items.forEach((item) => item.classList.remove("open"));
-            }
-        });
-
         const navLinks = Array.from(nav.querySelectorAll("a[href]")).filter((link) => !link.classList.contains("logo"));
         navLinks.forEach((link) => {
             const fallback = link.getAttribute("href");