diff --git a/operational b/operational
index c0a2b7301f50f603c6007b553ee70326e9f314d0..39cb01f2f0e785e22ed2f8b48b87b34692ce56c0 100644
--- a/operational
+++ b/operational
@@ -1,6 +1,6 @@
 * COMMENT -*- mode: org -*-
 #+Date: 2017-01-26
-Time-stamp: <2017-01-28>
+Time-stamp: <2017-01-29>
 #+STARTUP: content
 * notes                                                               :entry:
 ** 2017-01-28 visual design notes
@@ -129,6 +129,42 @@ the parent DOM.
 
 * current                                                             :entry:
 ** 
+** 2017-01-29 design a new UI for mobile. The emacs calc UI is not designed for mobile.
+Try copy from huawei built-in calc.
+
+[              ]
+[              ]
+[ >            ]
+
+C   /   *   <
+
+7   8   9   -
+
+4   5   6   +
+
+1   2   3   ret
+            ret
+0   U   .   ret
+
+- no scrolling at all.
+- stack display is 3-4 lines.
+- display size
+  nexus6p 412x732
+  nexus5x 412x732
+  iphone6 375x667
+  iphone6p 414x736
+  iphone5 320x568
+
+- make my UI auto adjust itself according to a container size.
+  container size is set to 98vh and 98vw.
+
+- left slide show full stack window.
+  right slide show full trail window.
+
+  like wordpress previous post and next post gesture.
+
+- 
+
 ** 2017-01-27 add some visual feedback when clicking a button. like in material design.
 ** 2017-01-27 UI problem: when input a very large number, #number-display and keyboard will grow.
 should set a max-width on #number-display.