diff --git a/src/App/App.tsx b/src/App/App.tsx
index 4a6408e..743d7fa 100644
--- a/src/App/App.tsx
+++ b/src/App/App.tsx
@@ -56,6 +56,28 @@ export function App() {
     scrollDownSidebar();
   }
 
+  function onBack() {
+    setTime(() => {
+      if (rtIdx !== undefined) {
+        if (rtIdx > 0)
+          return {
+            kind: "paused",
+            simtime: rt[rtIdx-1].simtime,
+          }
+      }
+      return { kind: "paused", simtime: 0 };
+    });
+    setRTIdx(rtIdx => {
+      if (rtIdx !== undefined) {
+        if (rtIdx > 0)
+          return rtIdx - 1;
+        else
+          return 0;
+      }
+      else return undefined;
+    })
+  }
+
   function scrollDownSidebar() {
     if (refRightSideBar.current) {
       const el = refRightSideBar.current;
@@ -128,15 +150,21 @@ export function App() {
         borderBottom: 1,
         borderColor: "divider",
         alignItems: 'center',
+        flex: '0 0 content',
       }}>
       <TopPanel
         rt={rtIdx === undefined ? undefined : rt[rtIdx]}
-        {...{ast, time, setTime, onInit, onClear, onRaise, mode, setMode}}
+        {...{rtIdx, ast, time, setTime, onInit, onClear, onRaise, onBack, mode, setMode}}
       />
     </Box>
-    <Stack direction="row" sx={{height:'calc(100vh - 64px)'}}>
+    <Stack direction="row" sx={{
+      overflow: 'auto',
+      }}>
       {/* main */}
-      <Box sx={{flexGrow:1, overflow:'auto'}}>
+      <Box sx={{
+        flexGrow:1,
+        overflow:'auto',
+      }}>
         <VisualEditor {...{ast, setAST, rt: rt.at(rtIdx!), setRT, errors, setErrors, mode, highlightActive, highlightTransitions}}/>
       </Box>
       {/* right sidebar */}
@@ -145,7 +173,6 @@ export function App() {
           borderLeft: 1,
           borderColor: "divider",
           flex: '0 0 content',
-          height: 'calc(100vh-32px)',
           overflow: "auto",
         }}>
           <ShowAST {...{...ast, rt: rt.at(rtIdx!), highlightActive}}/>
@@ -155,7 +182,9 @@ export function App() {
           </div>
         </Box>
     </Stack>
-    <Box>
+    <Box sx={{
+      flex: '0 0 content',
+    }}>
       <BottomPanel {...{errors}}/>
     </Box>
   </Stack>;
diff --git a/src/App/BottomPanel.css b/src/App/BottomPanel.css
index ceb412e..bbe185e 100644
--- a/src/App/BottomPanel.css
+++ b/src/App/BottomPanel.css
@@ -1,3 +1,9 @@
 .errorStatus {
-  color: rgb(230,0,0);
+  /* background-color: rgb(230,0,0); */
+  background-color: var(--error-color);
+  color: white;
+}
+
+.bottom {
+  background-color: lightyellow;
 }
\ No newline at end of file
diff --git a/src/App/BottomPanel.tsx b/src/App/BottomPanel.tsx
index f7cde46..b892f8a 100644
--- a/src/App/BottomPanel.tsx
+++ b/src/App/BottomPanel.tsx
@@ -1,10 +1,22 @@
+import { useEffect, useState } from "react";
 import { TraceableError } from "../statecharts/parser";
 
 import "./BottomPanel.css";
 
 export function BottomPanel(props: {errors: TraceableError[]}) {
-  return <div className="toolbar">
-    <div className="errorStatus">{
-      props.errors.length>0 && <>{props.errors.length} errors {props.errors.map(({message})=>message).join(',')}</>}</div>
+  const [greeting, setGreeting] = useState("Welcome to StateBuddy, buddy!");
+
+  useEffect(() => {
+    setTimeout(() => {
+      setGreeting("");
+    }, 2000);
+  }, []);
+
+  return <div className="toolbar bottom">
+    <>{greeting}</>
+    {props.errors.length > 0 &&
+      <div className="errorStatus">
+        {props.errors.length>0 && <>{props.errors.length} errors: {props.errors.map(({message})=>message).join(', ')}</>}
+      </div>}
   </div>;
 }
\ No newline at end of file
diff --git a/src/App/KeyInfo.tsx b/src/App/KeyInfo.tsx
index 09afde6..9e7fc73 100644
--- a/src/App/KeyInfo.tsx
+++ b/src/App/KeyInfo.tsx
@@ -2,10 +2,10 @@ import { Stack } from "@mui/material";
 
 export function KeyInfoVisible(props: {keyInfo, children}) {
   return <Stack style={{display: "inline-block"}}>
-    <div style={{fontSize:11, height: 16, textAlign:"center"}}>
+    <div style={{fontSize:11, height: 18, textAlign:"center", paddingLeft: 3, paddingRight: 3}}>
       {props.keyInfo}
     </div>
-    <div>
+    <div style={{textAlign:"center"}}>
       {props.children}
     </div>
   </Stack>
diff --git a/src/App/TopPanel.tsx b/src/App/TopPanel.tsx
index 4bab859..bdc046a 100644
--- a/src/App/TopPanel.tsx
+++ b/src/App/TopPanel.tsx
@@ -8,7 +8,7 @@ import PauseIcon from '@mui/icons-material/Pause';
 import PlayArrowIcon from '@mui/icons-material/PlayArrow';
 import BoltIcon from '@mui/icons-material/Bolt';
 import SkipNextIcon from '@mui/icons-material/SkipNext';
-import TrendingFlatIcon from '@mui/icons-material/TrendingFlat';
+import SkipPreviousIcon from '@mui/icons-material/SkipPrevious';import TrendingFlatIcon from '@mui/icons-material/TrendingFlat';
 import AccessAlarmIcon from '@mui/icons-material/AccessAlarm';
 import StopIcon from '@mui/icons-material/Stop';
 import UndoIcon from '@mui/icons-material/Undo';
@@ -20,11 +20,13 @@ import { KeyInfoHidden, KeyInfoVisible } from "./KeyInfo";
 
 export type TopPanelProps = {
   rt?: BigStep,
+  rtIdx?: number,
   time: TimeMode,
   setTime: Dispatch<SetStateAction<TimeMode>>,
   onInit: () => void,
   onClear: () => void,
   onRaise: (e: string, p: any) => void,
+  onBack: () => void,
   ast: Statechart,
   mode: InsertMode,
   setMode: Dispatch<SetStateAction<InsertMode>>,
@@ -61,7 +63,7 @@ function HistoryIcon(props: {kind: "shallow"|"deep"}) {
 }
 
 
-export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode, setMode}: TopPanelProps) {
+export function TopPanel({rt, rtIdx, time, setTime, onInit, onClear, onRaise, onBack, ast, mode, setMode}: TopPanelProps) {
   const [displayTime, setDisplayTime] = useState("0.000");
   const [timescale, setTimescale] = useState(1);
   const [showKeys, setShowKeys] = useState(true);
@@ -99,6 +101,10 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
         e.preventDefault();
         setShowKeys(show => !show);
       }
+      if (e.key === "Backspace") {
+        e.preventDefault();
+        onBack();
+      }
     };
     window.addEventListener("keydown", onKeyDown);
     return () => {
@@ -186,9 +192,20 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
   return <>
     <div className="toolbar">
 
-    <div style={{display:'inline-block'}}>
     <div style={{display:'inline-block'}}>
 
+    <div style={{display:'inline-block'}}>
+    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Z</kbd></>}>
+    <button title="undo"><UndoIcon fontSize="small"/></button>
+    </KeyInfo>
+    <KeyInfo keyInfo={<><kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>Z</kbd></>}>
+    <button title="redo"><RedoIcon fontSize="small"/></button>
+    </KeyInfo>
+    </div>
+
+    &emsp;
+
+    <div style={{display:'inline-block'}}>
     {([
       ["and", "AND-states", <RountangleIcon kind="and"/>, <kbd>A</kbd>],
       ["or", "OR-states", <RountangleIcon kind="or"/>, <kbd>O</kbd>],
@@ -205,7 +222,6 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
         className={mode===m ? "active":""}
         onClick={() => setMode(m)}
       >{buttonTxt}</button></KeyInfo>)}
-
     </div>
 
     &emsp;
@@ -221,7 +237,7 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
 
     &emsp;
 
-    <KeyInfo keyInfo={<kbd>Space</kbd>}>
+    <KeyInfo keyInfo={<><kbd>Space</kbd> toggles</>}>
       <button title="pause the simulation" disabled={!rt || time.kind==="paused"} className={(rt && time.kind==="paused") ? "active":""} onClick={() => onChangePaused(true, performance.now())}><PauseIcon fontSize="small"/></button>
       <button title="run the simulation in real time" disabled={!rt || time.kind==="realtime"} className={(rt && time.kind==="realtime") ? "active":""} onClick={() => onChangePaused(false, performance.now())}><PlayArrowIcon fontSize="small"/></button>
     </KeyInfo>
@@ -253,6 +269,12 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
     <button title="advance time just enough for the next timer to elapse" disabled={nextTimedTransition===undefined} onClick={onSkip}><SkipNextIcon fontSize="small"/><AccessAlarmIcon fontSize="small"/></button>
     </KeyInfo>
 
+    &emsp; 
+    <KeyInfo keyInfo={<kbd>Backspace</kbd>}>
+      <button title="undo last step (go back in time)" 
+      disabled={rtIdx===undefined || rtIdx===0} onClick={onBack}><SkipPreviousIcon fontSize="small"/></button>
+    </KeyInfo>
+
     </div>
 
     &emsp;
@@ -291,7 +313,7 @@ export function TopPanel({rt, time, setTime, onInit, onClear, onRaise, ast, mode
     <div style={{display:"inline-block"}}>
     <KeyInfo keyInfo={<kbd>~</kbd>}>
     <input id="checkbox-keys" type="checkbox" checked={showKeys} onChange={e => setShowKeys(e.target.checked)}></input>
-    <label for="checkbox-keys">shortcuts</label>
+    <label for="checkbox-keys">see shortcuts</label>
     </KeyInfo>
     </div>
 
diff --git a/src/VisualEditor/VisualEditor.css b/src/VisualEditor/VisualEditor.css
index f9d982e..619125a 100644
--- a/src/VisualEditor/VisualEditor.css
+++ b/src/VisualEditor/VisualEditor.css
@@ -39,19 +39,12 @@
   /* fill: rgba(0, 0, 255, 0.2); */
 }
 .rountangle.error {
-  stroke: rgb(230,0,0);
+  stroke: var(--error-color);
 }
 .rountangle.active {
-  /* fill: rgb(255, 140, 0); */
-  /* fill-opacity: 0.2; */
-  /* stroke: rgb(100, 149, 237); */
-  /* stroke:  */
   stroke: rgb(192, 125, 0);
   fill:rgb(255, 251, 244);
-  /* fill: lightgrey; */
-  /* color: white; */
-  filter: drop-shadow( 0px 0px 3px rgba(192, 125, 0, 0.856));
-  /* stroke-width: 3px; */
+  filter: drop-shadow( 0px 0px 3px rgba(192, 125, 0, 0.85));
 }
 
 .selected:hover:not(:active) {
@@ -166,7 +159,7 @@ text.helper:hover {
 }
 
 .arrow.error {
-  stroke: rgb(230,0,0);
+  stroke: var(--error-color);
 }
 .arrow.fired {
   stroke: rgb(192, 125, 0);
@@ -174,7 +167,7 @@ text.helper:hover {
 }
 
 text.error, tspan.error {
-  fill: rgb(230,0,0);
+  fill: var(--error-color);
   font-weight: 600;
 }
 
diff --git a/src/VisualEditor/VisualEditor.tsx b/src/VisualEditor/VisualEditor.tsx
index d5d6c80..3f657dc 100644
--- a/src/VisualEditor/VisualEditor.tsx
+++ b/src/VisualEditor/VisualEditor.tsx
@@ -314,7 +314,8 @@ export function VisualEditor({ast, setAST, rt, errors, setErrors, mode, highligh
   const onMouseMove = (e: {pageX: number, pageY: number}) => {
     const currentPointer = getCurrentPointer(e);
     if (dragging) {
-      const pointerDelta = subtractV2D(currentPointer, dragging.lastMousePos);
+      // const pointerDelta = subtractV2D(currentPointer, dragging.lastMousePos);
+      const pointerDelta = {x: e.movementX, y: e.movementY};
       setState(state => ({
         ...state,
         rountangles: state.rountangles.map(r => {
diff --git a/src/index.css b/src/index.css
index c54e9a7..cf0a025 100644
--- a/src/index.css
+++ b/src/index.css
@@ -4,6 +4,11 @@ html, body {
   font-family: Roboto, sans-serif;
 }
 
+body {
+  /* --error-color: darkred; */
+  --error-color: rgb(163, 0, 0);
+}
+
 div#root {
   height: 100%;
 }
@@ -18,7 +23,7 @@ kbd {
   border: 0.8px solid #aaa;
   border-radius: 4px;
   background: linear-gradient(#ebebeb, #fff);
-  box-shadow: inset 0 -2px 0 #aaa;
+  box-shadow: inset 0 -1.5px 0 #aaa;
   vertical-align: middle;
   user-select: none;
 }
@@ -38,4 +43,4 @@ input {
 
 label {
   user-select: none;
-}
\ No newline at end of file
+}