diff --git a/src/VisualEditor/VisualEditor.css b/src/VisualEditor/VisualEditor.css
index ce04107..af828c4 100644
--- a/src/VisualEditor/VisualEditor.css
+++ b/src/VisualEditor/VisualEditor.css
@@ -36,7 +36,9 @@ text.highlight {
 }
 
 .rountangle:hover {
-  /* fill: lightgrey; */
+  /* stroke: darkcyan; */
+  /* stroke-opacity: 0.2; */
+  /* fill: #eee; */
   /* stroke-width: 4px; */
   /* cursor: grab; */
 }
@@ -65,15 +67,29 @@ text.highlight {
   stroke-width: 16px;
 }
 .lineHelper:hover {
-  stroke: rgba(0, 255, 0, 0.2);
+  stroke: darkcyan;
+  stroke-opacity: 0.2;
   cursor: grab;
 }
 
+.pathHelper {
+  fill: none;
+  stroke: rgba(0, 0, 0, 0);
+  stroke-width: 16px;
+}
+.pathHelper:hover {
+  stroke: darkcyan;
+  stroke-opacity: 0.2;
+  cursor: grab;
+}
+
+
 .circleHelper {
   fill: rgba(0, 0, 0, 0);
 }
 .circleHelper:hover {
-  fill: rgba(0, 255, 0, 0.2);
+  fill: darkcyan;
+  fill-opacity: 0.2;
   cursor: grab;
 }
 
diff --git a/src/VisualEditor/VisualEditor.tsx b/src/VisualEditor/VisualEditor.tsx
index 644b6bc..e71b54f 100644
--- a/src/VisualEditor/VisualEditor.tsx
+++ b/src/VisualEditor/VisualEditor.tsx
@@ -9,6 +9,7 @@ import { parseStatechart } from "./parser";
 import { CORNER_HELPER_OFFSET, CORNER_HELPER_RADIUS, MIN_ROUNTANGLE_SIZE, ROUNTANGLE_RADIUS } from "./parameters";
 
 import * as lz4 from "@nick/lz4";
+import { initialize } from "./interpreter";
 
 
 type DraggingState = {
@@ -138,6 +139,9 @@ export function VisualEditor() {
       const [statechart, errors] = parseStatechart(state);
       console.log('statechart: ', statechart, 'errors:', errors);
       setErrors(errors);
+
+      const rt = initialize(statechart);
+      console.log('runtime:', rt);
     }, 100);
     return () => clearTimeout(timeout);
   }, [state]);
@@ -183,7 +187,7 @@ export function VisualEditor() {
             ...state,
             texts: [...state.texts, {
               uid: newID,
-              text: "Double-click to edit text",
+              text: "// Double-click to edit",
               topLeft: currentPointer,
             }],
             nextID: state.nextID+1,
@@ -538,7 +542,7 @@ export function VisualEditor() {
       const commonProps = {
         "data-uid": txt.uid,
         "data-parts": "text",
-        textAnchor: "middle",
+        textAnchor: "middle" as "middle",
         className: 
           (selection.find(s => s.uid === txt.uid)?.parts?.length ? "selected":"")
           +(textsToHighlight.hasOwnProperty(txt.uid)?" highlight":""),
@@ -763,12 +767,12 @@ export function ArrowSVG(props: {arrow: Arrow, selected: string[], errors: strin
 
     {props.errors.length>0 && <text className="error" x={(start.x+end.x)/2+5} y={(start.y+end.y)/2} data-uid={uid} data-parts="start end">{props.errors.join(' ')}</text>}
 
-    <line
-      className="lineHelper"
-      x1={start.x}
-      y1={start.y}
-      x2={end.x}
-      y2={end.y}
+    <path
+      className="pathHelper"
+      // markerEnd='url(#arrowEnd)'
+      d={`M ${start.x} ${start.y}
+            ${arcOrLine}
+            ${end.x} ${end.y}`}
       data-uid={uid}
       data-parts="start end"
     />
diff --git a/src/VisualEditor/interpreter.ts b/src/VisualEditor/interpreter.ts
index 429ceab..467ee07 100644
--- a/src/VisualEditor/interpreter.ts
+++ b/src/VisualEditor/interpreter.ts
@@ -1,27 +1,126 @@
 import { ConcreteState, Statechart } from "./ast";
+import { Action, Expression } from "./label_ast";
+import { Environment, RaisedEvents, Mode, RT_Statechart, initialRaised } from "./runtime_types";
 
 export function initialize(ast: Statechart): RT_Statechart {
-  const rt_root = recursiveEnter(ast.root) as RT_OrState;
+  const {mode, environment, raised} = enter(ast.root, {
+    environment: new Map(),
+    raised: initialRaised,
+  });
   return {
-    root: rt_root,
-    variables: new Map(),
+    mode,
+    environment,
+    inputEvents: [],
+    ...raised,
   };
 }
 
-export function recursiveEnter(state: ConcreteState): RT_ConcreteState {
+type ActionScope = {
+  environment: Environment,
+  raised: RaisedEvents,
+};
+
+export function enter(state: ConcreteState, rt: ActionScope): ({mode: Mode} & ActionScope) {
+  let {environment, raised} = rt;
+  for (const action of state.entryActions) {
+    ({environment, raised} = execAction(action, {environment, raised}));
+  }
   if (state.kind === "and") {
-    return {
-      kind: "and",
-      children: state.children.map(child => recursiveEnter(child)),
-    };
+    const mode: {[uid:string]: Mode} = {};
+    for (const child of state.children) {
+      let childMode;
+      ({mode: childMode, environment, raised} = enter(child, {environment, raised}));
+      mode[child.uid] = childMode;
+    }
+    return { mode, environment, raised };
   }
-  else {
-    const currentState = state.initial[0][1];
-    return {
-      kind: "or",
-      current: currentState.uid,
-      current_rt: recursiveEnter(currentState),
-    };
+  else if (state.kind === "or") {
+    const mode: {[uid:string]: Mode} = {};
+    // same as AND-state, but we only enter the initial state(s)
+    for (const [_, child] of state.initial) {
+      let childMode;
+      ({mode: childMode, environment, raised} = enter(child, {environment, raised}));
+      mode[child.uid] = childMode;
+      return { mode, environment, raised };
+    }
   }
+  throw new Error("should never reach here");
+}
+
+export function execAction(action: Action, rt: ActionScope): ActionScope {
+  if (action.kind === "assignment") {
+    const rhs = evalExpr(action.rhs, rt.environment);
+    const newEnvironment = new Map(rt.environment);
+    newEnvironment.set(action.lhs, rhs);
+    return {
+      ...rt,
+      environment: newEnvironment,
+    };
+  }
+  else if (action.kind === "raise") {
+    if (action.event.startsWith('_')) {
+      // append to internal events
+      return {
+        ...rt,
+        raised: {
+          ...rt.raised,
+          internalEvents: [...rt.raised.internalEvents, action.event]},
+      };
+    }
+    else {
+      // append to output events
+      return {
+        ...rt,
+        raised: {
+          ...rt.raised,
+          outputEvents: [...rt.raised.outputEvents, action.event],
+        },
+      }
+    }
+  }
+  throw new Error("should never reach here");
+}
+
+
+const UNARY_OPERATOR_MAP: Map<string, (x:any)=>any> = new Map([
+  ["!", x => !x],
+  ["-", x => -x as any],
+]);
+
+const BINARY_OPERATOR_MAP: Map<string, (a:any,b:any)=>any> = new Map([
+  ["+", (a,b) => a+b],
+  ["-", (a,b) => a-b],
+  ["*", (a,b) => a*b],
+  ["/", (a,b) => a/b],
+  ["&&", (a,b) => a&&b],
+  ["||", (a,b) => a||b],
+  ["==", (a,b) => a==b],
+  ["<=", (a,b) => a<=b],
+  [">=", (a,b) => a>=b],
+  ["<", (a,b) => a<b],
+  [">", (a,b) => a>b],
+]);
+
+export function evalExpr(expr: Expression, environment: Environment): any {
+  if (expr.kind === "literal") {
+    return expr.value;
+  }
+  else if (expr.kind === "ref") {
+    const found = environment.get(expr.variable);
+    if (found === undefined) {
+      throw new Error(`variable '${expr.variable}' does not exist in environment`)
+    }
+    return found;
+  }
+  else if (expr.kind === "unaryExpr") {
+    const arg = evalExpr(expr.expr, environment);
+    return UNARY_OPERATOR_MAP.get(expr.operator)!(arg);
+  }
+  else if (expr.kind === "binaryExpr") {
+    const argA = evalExpr(expr.lhs, environment);
+    const argB = evalExpr(expr.rhs, environment);
+    return BINARY_OPERATOR_MAP.get(expr.operator)!(argA,argB);
+  }
+  throw new Error("should never reach here");
 }
 
diff --git a/src/VisualEditor/parser.ts b/src/VisualEditor/parser.ts
index 02b876c..b19b2ec 100644
--- a/src/VisualEditor/parser.ts
+++ b/src/VisualEditor/parser.ts
@@ -196,7 +196,7 @@ export function parseStatechart(state: VisualEditorState): [Statechart, [string,
         errorShapes.push([text.uid, {
           message: "states can only have entry/exit triggers",
           location: {start: {offset: 0}, end: {offset: text.text.length}},
-        } as unknown as string]);
+        }]);
       }
 
     }
@@ -235,9 +235,7 @@ function findVariables(expr: Expression): Set<string> {
   else if (expr.kind === "binaryExpr") {
     return findVariables(expr.lhs).union(findVariables(expr.rhs));
   }
-  else if (expr.kind === "literal") {
-    return new Set();
-  }
+  return new Set();
 }
 
 function findVariablesAction(action: Action): Set<string> {
diff --git a/src/VisualEditor/runtime_types.ts b/src/VisualEditor/runtime_types.ts
index d7af957..093c340 100644
--- a/src/VisualEditor/runtime_types.ts
+++ b/src/VisualEditor/runtime_types.ts
@@ -1,18 +1,28 @@
+// modal configuration: maps child-uid to modal configuration of the child
+// for OR-states, only the modal configuration of the current state is kept
+// for AND-states, the modal configuration of every child is kept
+// for basic states (= empty AND-states), the modal configuration is just an empty object
+export type Mode = {[uid:string]: Mode};
 
-type RT_ConcreteState = RT_OrState | RT_AndState;
+export type Environment = ReadonlyMap<string, any>; // variable name -> value
 
-type RT_OrState = {
-  kind: "or";
-  current: string;
-  current_rt: RT_ConcreteState; // keep the runtime configuration only of the current state
+export type RT_Statechart = {
+  mode: Mode;
+  environment: Environment;
+  // history: // TODO
+
+  inputEvents: string[];
+} & RaisedEvents;
+
+export type RaisedEvents = {
+  internalEvents: string[];
+  outputEvents: string[];
+};
+
+export const initialRaised: RaisedEvents = {
+  internalEvents: [],
+  outputEvents: [],
 }
 
-type RT_AndState = {
-  kind: "and";
-  children: RT_ConcreteState[]; // keep the runtime configuration of every child
-}
-
-type RT_Statechart = {
-  root: RT_OrState;
-  variables: Map<string, any>;
-}
+// export type RT_Events = {
+// };