diff --git a/lib/builtin-themes.ts b/lib/builtin-themes.ts
index 6a7eb510..c2974762 100644
--- a/lib/builtin-themes.ts
+++ b/lib/builtin-themes.ts
@@ -977,6 +977,37 @@ body[data-theme-skin="builtin-vnclagoon"] h2,
 body[data-theme-skin="builtin-vnclagoon"] h3 {
   font-family: "Syne", "DM Sans", sans-serif;
   letter-spacing: -0.01em;
+}
+
+/* ── Login card — VNClagoon treatment ─────────────────────────── */
+/* Solid navy card (var --color-card) with a cyan hairline and a thin cyan
+   accent strip along the top. The login card is the only .rounded-2xl with
+   .bg-background/80 + .backdrop-blur-sm, so this scopes cleanly to it. */
+body[data-theme-skin="builtin-vnclagoon"] .rounded-2xl.border.bg-background\\/80.backdrop-blur-sm {
+  position: relative;
+  background-color: var(--color-card) !important;
+  border-color: rgba(0, 212, 255, 0.16) !important;
+}
+body[data-theme-skin="builtin-vnclagoon"] .rounded-2xl.border.bg-background\\/80.backdrop-blur-sm::before {
+  content: "";
+  position: absolute;
+  left: 0;
+  right: 0;
+  top: 0;
+  height: 3px;
+  background: linear-gradient(90deg, transparent, #00d4ff 35%, #00d4ff 65%, transparent);
+}
+/* Depth + soft cyan glow, dark-first */
+.dark body[data-theme-skin="builtin-vnclagoon"] .rounded-2xl.border.bg-background\\/80.backdrop-blur-sm {
+  box-shadow:
+    0 24px 60px -24px rgba(0, 0, 0, 0.7),
+    0 0 0 1px rgba(0, 212, 255, 0.06),
+    0 0 48px -16px rgba(0, 212, 255, 0.22) !important;
+}
+/* Ambient cyan wash behind the card on the login page */
+.dark body[data-theme-skin="builtin-vnclagoon"] .min-h-screen.bg-gradient-to-br {
+  background-color: var(--color-background) !important;
+  background-image: radial-gradient(56rem 38rem at 50% -12%, rgba(0, 212, 255, 0.10), transparent 60%) !important;
 }`;
 
 export const BUILTIN_THEMES: InstalledTheme[] = [