diff --git a/app.wxss b/app.wxss
index 0f3859d..9946b19 100644
--- a/app.wxss
+++ b/app.wxss
@@ -130,5 +130,10 @@ image {
 
 @keyframes pageIn {
   from { opacity: 0; transform: translateY(20rpx); }
-  to   { opacity: 1; transform: translateY(0); }
+  /* `none` (not translateY(0)) so the finished animation leaves NO transform
+     on .container - any non-none transform creates a containing block that
+     demotes descendant position:fixed to relative-to-container, breaking
+     full-screen modals (day-detail / plan-editor / completion) once the
+     page scrolls past one viewport height. */
+  to   { opacity: 1; transform: none; }
 }