diff --git a/assets/css/style.css b/assets/css/style.css
index 776b52d..79bef7e 100644
--- a/assets/css/style.css
+++ b/assets/css/style.css
@@ -246,12 +246,13 @@ nav a {
 .portal-nav .portal-nav__subgroup>.portal-submenu-nested {
     list-style: none;
     margin: 0;
-    padding: 8px 10px;
+    margin-left: -12px;
+    padding: 8px 10px 8px 22px;
     display: none;
     flex-direction: column;
     gap: 4px;
     position: absolute;
-    left: calc(100% + 6px);
+    left: 100%;
     top: 0;
     min-width: 216px;
     width: max-content;
@@ -321,12 +322,13 @@ nav a {
 .portal-nav .portal-submenu-nested--tier3 {
     list-style: none;
     margin: 0;
-    padding: 8px 10px;
+    margin-left: -12px;
+    padding: 8px 10px 8px 22px;
     display: none;
     flex-direction: column;
     gap: 2px;
     position: absolute;
-    left: calc(100% + 6px);
+    left: 100%;
     top: 0;
     min-width: 200px;
     width: max-content;
@@ -336,11 +338,14 @@ nav a {
     box-shadow: 0 14px 36px rgba(0, 0, 0, 0.16);
     border: 1px solid rgba(0, 0, 0, 0.07);
     z-index: 102;
+    overflow: visible;
     box-sizing: border-box;
 }
 
 .portal-nav .portal-nav__subgroup--nested:hover>.portal-submenu-nested--tier3,
-.portal-nav .portal-nav__subgroup--nested:focus-within>.portal-submenu-nested--tier3 {
+.portal-nav .portal-nav__subgroup--nested:focus-within>.portal-submenu-nested--tier3,
+.portal-nav .portal-submenu-nested--tier3:hover,
+.portal-nav .portal-submenu-nested--tier3:focus-within {
     display: flex;
 }
 
@@ -348,16 +353,46 @@ nav a {
 
     .portal-nav .portal-nav__subgroup>.portal-submenu-nested {
         position: absolute !important;
-        left: calc(100% + 6px) !important;
+        left: 100% !important;
         top: 0 !important;
         right: auto !important;
+        margin-left: -12px !important;
+        padding-left: 22px !important;
     }
 
     .portal-nav .portal-submenu-nested--tier3 {
         position: absolute !important;
-        left: calc(100% + 6px) !important;
+        left: 100% !important;
         top: 0 !important;
         right: auto !important;
+        margin-left: -12px !important;
+        padding-left: 22px !important;
+    }
+
+    /* 滑向第三層時，左側透明 padding 接軌上一列，避免空隙斷 hover */
+    .portal-nav .portal-nav__subgroup--nested:hover,
+    .portal-nav .portal-nav__subgroup--nested:focus-within {
+        z-index: 111;
+    }
+
+    .portal-nav .portal-submenu .portal-nav__subgroup::after {
+        content: "";
+        position: absolute;
+        left: 100%;
+        top: 0;
+        width: 18px;
+        height: 100%;
+        z-index: 90;
+    }
+
+    .portal-nav .portal-nav__subgroup--nested::before {
+        content: "";
+        position: absolute;
+        left: 100%;
+        top: 0;
+        width: 18px;
+        height: 100%;
+        z-index: 110;
     }
 }
 
@@ -1540,7 +1575,11 @@ footer a .mark_b {
 
     .map-page .portal-nav .portal-nav__subgroup>.portal-submenu-nested {
         left: auto !important;
-        right: calc(100% + 6px) !important;
+        right: 100% !important;
+        margin-left: 0 !important;
+        margin-right: -12px !important;
+        padding-left: 10px !important;
+        padding-right: 22px !important;
     }
 
     .map-page .portal-nav .portal-nav__subgroup-head--nested::after {
@@ -1550,7 +1589,11 @@ footer a .mark_b {
 
     .map-page .portal-nav li.portal-nav__subgroup--nested>.portal-submenu-nested--tier3 {
         left: auto !important;
-        right: calc(100% + 6px) !important;
+        right: 100% !important;
+        margin-left: 0 !important;
+        margin-right: -12px !important;
+        padding-left: 10px !important;
+        padding-right: 22px !important;
     }
 }
 
diff --git a/assets/js/portal-nav.js b/assets/js/portal-nav.js
index 48599e5..1e497df 100644
--- a/assets/js/portal-nav.js
+++ b/assets/js/portal-nav.js
@@ -20,7 +20,7 @@
     ];
 
     /** 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 = 480;
+    const SUBMENU_CLOSE_DELAY_MS = 650;
 
     function pickSoonPhrase() {
         return NAV_SOON_PHRASES[Math.floor(Math.random() * NAV_SOON_PHRASES.length)];
@@ -296,18 +296,38 @@
                 item.classList.add("open");
             };
 
+            const cancelClose = () => {
+                if (closeTimer) {
+                    window.clearTimeout(closeTimer);
+                    closeTimer = null;
+                }
+            };
+
             const scheduleClose = () => {
+                cancelClose();
                 closeTimer = window.setTimeout(() => item.classList.remove("open"), SUBMENU_CLOSE_DELAY_MS);
             };
 
+            const leaveUnlessStillInside = (event) => {
+                const next = event.relatedTarget;
+                if (next instanceof Node && item.contains(next)) return;
+                scheduleClose();
+            };
+
             item.addEventListener("mouseenter", openItem);
-            item.addEventListener("mouseleave", scheduleClose);
+            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);
+            });
             trigger.addEventListener("focus", openItem);
 
             trigger.addEventListener("click", (event) => {
                 const isSoon = trigger.getAttribute("data-coming-soon") === "true";
 
-                if (window.innerWidth <= 1024) {
+                if (window.innerWidth <= 767) {
                     event.preventDefault();
                     if (!isSoon && !item.classList.contains("coming-soon")) {
                         item.classList.toggle("open");