diff --git a/frontend/src/Editor.svelte b/frontend/src/Editor.svelte
index a4f1673..9519902 100644
--- a/frontend/src/Editor.svelte
+++ b/frontend/src/Editor.svelte
@@ -1,41 +1,27 @@
 <script type="ts">
   import Graph from "./Graph.svelte";
   import { nonNull } from "./helpers";
-  import { grabAssignment } from "./ksp-task-grabber";
   import type { TaskDescriptor, TasksFile } from "./task-loader";
-  import { saveTasks, createTaskMap, getCategories } from "./task-loader";
+  import { saveTasks, getCategories } from "./task-loader";
   import TaskDisplay from "./TaskDisplay.svelte";
 
   export let tasks: TasksFile;
 
-  let selectedTask: string | null = null;
-  let clickedTask: string | null = null;
   let repulsionForce: number = -600;
   let clicked: string[] = [];
+  let graph: Graph;
+  let currentTask: TaskDescriptor | null = null;
 
   function clickTask(e: CustomEvent<TaskDescriptor>) {
-    // sanity check
-    if (selectedTask == null) {
-      alert("tohle je divny event");
-      return;
-    }
-
     // ukladani seznamu poslednich kliknuti
-    clicked.push(selectedTask);
+    clicked = [...clicked, e.detail.id];
     if (clicked.length > 3)
       clicked = clicked.slice(clicked.length - 3, clicked.length);
-    clicked = clicked;
-
-    // trackovani, kam se naposledy kliknulo
-    if (clickedTask == selectedTask) {
-      clickedTask = null;
-    } else {
-      clickedTask = selectedTask;
-    }
   }
 
-  $: taskMap = createTaskMap(tasks);
-  $: currentTask = clickedTask != null ? clickedTask : selectedTask;
+  function startHovering(e: CustomEvent<TaskDescriptor>) {
+    currentTask = e.detail;
+  }
 
   function addEdge() {
     if (clicked.length > 1) {
@@ -44,21 +30,15 @@
 
       tasks.tasks.forEach((t) => {
         if (t.id == first) {
-          t.requires.push(second);
-          t = t;
+          t.requires = [...t.requires, second];
         }
       });
       tasks = tasks;
-
-      // run simulation
-      graph.runSimulation()
     } else {
       alert("Nope, prvni musis nekam klikat...");
     }
   }
 
-  let graph: Graph
-
   async function saveCurrentState() {
     await saveTasks(tasks);
   }
@@ -122,8 +102,8 @@
       <Graph
         {tasks}
         {repulsionForce}
-        bind:selectedTask
         on:selectTask={clickTask}
+        on:preSelectTask={startHovering}
         bind:this={graph} />
     </div>
   </div>
@@ -133,7 +113,7 @@
       <div>
         <button on:click={addEdge}>Pridat hranu - posledni vyzaduje predposledni</button>
       </div>
-      <div><button on:click={toggleDivnaPromena}>Spustit simulaci</button></div>
+      <div><button on:click={graph.runSimulation}>Spustit simulaci</button></div>
       <div>
         Repulsion force: <input type="number" bind:value={repulsionForce} name="repulsionForceInput" max="1000" min="-10000" />
       </div>
@@ -143,14 +123,14 @@
     </div>
     <div class="taskDetails">
       {#if currentTask != null}
-        <h3>{currentTask}</h3>
-        <span>{nonNull(taskMap.get(currentTask)).comment}</span>
+        <h3>{currentTask.id}</h3>
+        <span>{nonNull(currentTask).comment}</span>
         <ul>
-          {#each getCategories(tasks, currentTask) as cat}
+          {#each getCategories(tasks, currentTask.id) as cat}
             <li>{cat}</li>
           {/each}
         </ul>
-        <TaskDisplay taskId={currentTask} />
+        <TaskDisplay taskId={currentTask.id} />
       {:else}
         <h3>Nothing selected...</h3>
       {/if}
diff --git a/frontend/src/Graph.svelte b/frontend/src/Graph.svelte
index 4f6a112..6307128 100644
--- a/frontend/src/Graph.svelte
+++ b/frontend/src/Graph.svelte
@@ -3,8 +3,8 @@
   import GraphEdge from "./GraphEdge.svelte";
   import { createEventDispatcher, onMount } from "svelte";
   import * as d3 from "d3";
-  import { createLinksFromTaskMap } from "./task-loader";
   import type { TasksFile, TaskDescriptor } from "./task-loader";
+  import { createNodesAndEdges } from "./graph-types";
 
   export let tasks: TasksFile;
   let hoveredTask: null | string = null;
@@ -16,8 +16,17 @@
   let clientWidth: number;
   let svgElement: SVGElement;
 
-  $: nodes = tasks.tasks;
-  $: edges = createLinksFromTaskMap(tasks);
+  // this prevents svelte from updating nodes and edges
+  // when we update nodes and edges
+  let [nodes, edges] = createNodesAndEdges(tasks);
+  function hack() {
+    [nodes, edges] = createNodesAndEdges(tasks);
+    runSimulation();
+  }
+  $: {
+    tasks;
+    hack();
+  }
 
   const eventDispatcher = createEventDispatcher();
 
@@ -32,9 +41,8 @@
       hoveredTask = task.id;
       eventDispatcher("preSelectTask", task);
     } else {
-      if (hoveredTask == task.id)
-        hoveredTask = null;
-        eventDispatcher("unPreSelectTask", task);
+      if (hoveredTask == task.id) hoveredTask = null;
+      eventDispatcher("unPreSelectTask", task);
     }
   };
 
@@ -83,6 +91,8 @@
     }
     let zoomer = d3.zoom().scaleExtent([0.1, 2]).on("zoom", zoomed);
     d3.select(container).call(zoomer);
+
+    runSimulation();
   });
 </script>
 
@@ -93,6 +103,8 @@
   }
 </style>
 
+{@debug tasks}
+
 <div bind:this={container} bind:clientHeight bind:clientWidth>
   <svg bind:this={svgElement}>
     <g>
@@ -103,8 +115,8 @@
         <GraphNode
           {task}
           on:taskClick
-          on:click={nodeClick(task)}
-          on:hoveringChange={nodeHover(task)} />
+          on:click={nodeClick(task.task)}
+          on:hoveringChange={nodeHover(task.task)} />
       {/each}
     </g>
   </svg>
diff --git a/frontend/src/GraphEdge.svelte b/frontend/src/GraphEdge.svelte
index 5ca8724..c56e8ab 100644
--- a/frontend/src/GraphEdge.svelte
+++ b/frontend/src/GraphEdge.svelte
@@ -1,9 +1,8 @@
 <script lang="ts">
     import type { SimulationLinkDatum } from "d3";
+    import type { TaskId } from "./graph-types";
   
-    import type { TaskDescriptor } from "./task-loader";
-  
-    export let edge: SimulationLinkDatum<TaskDescriptor>;
+    export let edge: SimulationLinkDatum<TaskId>;
   
     $: x1 = edge === undefined || edge.source === undefined || edge.source.x === undefined ? 0 : edge.source.x;
     $: y1 = edge === undefined || edge.source === undefined || edge.source.y === undefined ? 0 : edge.source.y;
diff --git a/frontend/src/GraphNode.svelte b/frontend/src/GraphNode.svelte
index 2e353e3..0c5f39d 100644
--- a/frontend/src/GraphNode.svelte
+++ b/frontend/src/GraphNode.svelte
@@ -1,8 +1,9 @@
 <script lang="ts">
   import { createEventDispatcher, onMount } from "svelte";
-  import type { TaskDescriptor } from "./task-loader";
+  import type { TaskId } from "./graph-types";
 
-  export let task: TaskDescriptor;
+
+  export let task: TaskId;
   let hovering: boolean = false;
   let text_element: SVGTextElement;
 
diff --git a/frontend/src/graph-types.ts b/frontend/src/graph-types.ts
new file mode 100644
index 0000000..0391c8b
--- /dev/null
+++ b/frontend/src/graph-types.ts
@@ -0,0 +1,45 @@
+import type { SimulationLinkDatum, SimulationNodeDatum } from "d3";
+import type { TaskDescriptor, TasksFile } from "./task-loader";
+import { createTaskMap } from "./task-loader";
+
+
+export type TaskId = {
+    id: string;
+    task: TaskDescriptor;
+} & SimulationNodeDatum;
+
+function createNodes(tasks: TasksFile, old?: TaskId[]): TaskId[] {
+    return tasks.tasks.map((t) => {
+        return { id: t.id, task: t };
+    });
+}
+
+export function createNodesAndEdges(tasks: TasksFile, oldNodes?, oldEdges?): [TaskId[], SimulationLinkDatum<TaskId>[]] {
+    let nodes = createNodes(tasks, oldNodes);
+
+    // create mapping from ID to node
+    let nodeMap = new Map<string, TaskId>();
+    for (let task of nodes) {
+        if (task.id in nodeMap) throw 'duplicate IDs';
+        nodeMap.set(task.id, task);
+    }
+
+    let links: SimulationLinkDatum<TaskId>[] = [];
+    for (const task of tasks.tasks) {
+        const src = nodeMap.get(task.id)!;
+        for (const id of task.requires) {
+            const t = nodeMap.get(id);
+
+            if (t === undefined) throw `missing task with id ${id}`;
+
+            const l: SimulationLinkDatum<TaskId> =
+            {
+                source: src,
+                target: t
+            };
+            links.push(l);
+        }
+    }
+
+    return [nodes, links];    
+}
diff --git a/frontend/src/task-loader.ts b/frontend/src/task-loader.ts
index 60890ff..e7556fa 100644
--- a/frontend/src/task-loader.ts
+++ b/frontend/src/task-loader.ts
@@ -4,8 +4,7 @@ export type TaskDescriptor = {
     id: string
     requires: string[]
     comment?: string
-} & SimulationNodeDatum
-
+}
 
 export type TasksFile = {
     tasks: TaskDescriptor[]
@@ -44,25 +43,6 @@ export function createTaskMap(tasks: TasksFile): TaskMap {
     return m;
 }
 
-export function createLinksFromTaskMap(tasks: TasksFile): SimulationLinkDatum<TaskDescriptor>[] {
-    let links: SimulationLinkDatum<TaskDescriptor>[] = [];
-
-    const taskMap = createTaskMap(tasks);
-
-    for (const task of tasks.tasks) {
-        for (const id of task.requires) {
-            const t = taskMap.get(id);
-
-            if (t === undefined) throw `missing task with id ${id}`;
-
-            const l: SimulationLinkDatum<TaskDescriptor> = { source: t, target: task };
-            links.push(l);
-        }
-    }
-
-    return links;
-}
-
 export function getCategories(tasks: TasksFile, taskId: string): string[] {
     let res: string[] = [];
     for (let [cat, ids] of Object.entries(tasks.clusters)) {