diff --git a/src/frontend/core/datas/Array1DData.js b/src/frontend/core/datas/Array1DData.js
index 6b7fb5ec3d537ebe05e3399d52520ba13dd360a4..44752c8c8cf0126f54921455649b67cbe7295fc8 100644
--- a/src/frontend/core/datas/Array1DData.js
+++ b/src/frontend/core/datas/Array1DData.js
@@ -7,14 +7,10 @@ class Array1DData extends Array2DData {
     this.chartData = null;
   }
 
-  render() {
-    super.render();
-    this.syncChartData();
-  }
-
   set(array1d = []) {
     const array2d = [array1d];
     super.set(array2d);
+    this.syncChartData();
   }
 
   notify(x, v) {
@@ -39,10 +35,7 @@ class Array1DData extends Array2DData {
   }
 
   syncChartData() {
-    if (this.chartData) {
-      this.chartData.data = this.data;
-      this.chartData.render();
-    }
+    if (this.chartData) this.chartData.data = this.data;
   }
 }
 
diff --git a/src/frontend/core/datas/Array2DData.js b/src/frontend/core/datas/Array2DData.js
index a2feeeb9d1e290b4531756ed8ff1dca96752bad6..9ff3802db422c0f112b8640b8bce9c557860a7dd 100644
--- a/src/frontend/core/datas/Array2DData.js
+++ b/src/frontend/core/datas/Array2DData.js
@@ -21,12 +21,10 @@ class Array2DData extends Data {
   notify(x, y, v = this.data[x][y].value) {
     this.data[x][y].value = v;
     this.data[x][y].notified = true;
-    this.render();
   }
 
   denotify(x, y) {
     this.data[x][y].notified = false;
-    this.render();
   }
 
   select(sx, sy, ex = sx, ey = sy) {
@@ -35,7 +33,6 @@ class Array2DData extends Data {
         this.data[x][y].selected = true;
       }
     }
-    this.render();
   }
 
   selectRow(x, sy, ey) {
@@ -52,7 +49,6 @@ class Array2DData extends Data {
         this.data[x][y].selected = false;
       }
     }
-    this.render();
   }
 
   deselectRow(x, sy, ey) {
diff --git a/src/frontend/core/datas/Data.js b/src/frontend/core/datas/Data.js
index 765224f0806d9e796130e2af8328bcc1693403a1..f6982cb1d946037706777484123193d3754cc7d1 100644
--- a/src/frontend/core/datas/Data.js
+++ b/src/frontend/core/datas/Data.js
@@ -29,7 +29,6 @@ class Data {
   }
 
   set() {
-    this.render();
   }
 
   wait() {
diff --git a/src/frontend/core/datas/GraphData.js b/src/frontend/core/datas/GraphData.js
index c575fe00301ff03f7b017866435c0577b4c7301b..819c8fd3d9bfd2d8bcb11618f9931001b8fbc5c6 100644
--- a/src/frontend/core/datas/GraphData.js
+++ b/src/frontend/core/datas/GraphData.js
@@ -1,5 +1,4 @@
 import { Data } from '/core/datas';
-import { GraphTracer } from '/core/tracers';
 import { distance } from '/common/util';
 import { tracerManager } from '/core';
 
@@ -24,105 +23,48 @@ class GraphData extends Data {
       edgeWeightGap: 4,
     };
     this.logData = null;
+    this.callLayout = { method: this.layoutCircle, args: [] };
   }
 
-  set(array2d = [], layout = GraphTracer.LAYOUT.CIRCLE, root = 0) {
-    const { directed, weighted } = this.options;
-    const { baseWidth, baseHeight, padding } = this.dimensions;
-    this.graph = new Graph([], [], directed);
+  set(array2d = []) {
+    const { weighted } = this.options;
+    this.nodes = [];
+    this.edges = [];
     for (let i = 0; i < array2d.length; i++) {
-      const id = i;
-      const weight = null;
-      const visitedCount = 0;
-      this.graph.addNode(id, weight, visitedCount);
+      this.addNode(i);
       for (let j = 0; j < array2d.length; j++) {
         const value = array2d[i][j];
         if (value) {
-          const source = i;
-          const target = j;
-          const weight = weighted ? value : null;
-          const visitedCount = 0;
-          this.graph.addEdge(source, target, weight, visitedCount);
+          this.addEdge(i, j, weighted ? value : null);
         }
       }
     }
-    const left = -baseWidth / 2 + padding;
-    const top = -baseHeight / 2 + padding;
-    const right = baseWidth / 2 - padding;
-    const bottom = baseHeight / 2 - padding;
-    const width = right - left;
-    const height = bottom - top;
-    const rect = { left, top, right, bottom, width, height };
-    switch (layout) {
-      case GraphTracer.LAYOUT.CIRCLE:
-        this.graph.layoutCircle(rect);
-        break;
-      case GraphTracer.LAYOUT.TREE:
-        this.graph.layoutTree(rect, root);
-        break;
-      case GraphTracer.LAYOUT.RANDOM:
-        this.graph.layoutRandom(rect);
-        break;
-      case GraphTracer.LAYOUT.NONE:
-      default:
-        break;
-    }
+    this.layout();
     super.set();
   }
 
-  visit(target, source, weight) {
-    this.visitOrLeave(target, source, weight, true);
-  }
-
-  leave(target, source, weight) {
-    this.visitOrLeave(target, source, weight, false);
+  addNode(id, weight = null, visitedCount = 0, selectedCount = 0, x = 0, y = 0) {
+    if (this.findNode(id)) return;
+    this.nodes.push({ id, weight, visitedCount, selectedCount, x, y });
+    this.layout();
   }
 
-  visitOrLeave(target, source, weight, visit) {
-    const edge = this.graph.findEdge(source, target);
-    if (edge) edge.visitedCount += visit ? 1 : -1;
-    const node = this.graph.findNode(target);
-    node.weight = weight;
-    node.visitedCount += visit ? 1 : -1;
-    this.render();
-    if (this.logData) {
-      this.logData.print(visit ? (source || '') + ' -> ' + target : (source || '') + ' <- ' + target);
-    }
+  addEdge(source, target, weight = null, visitedCount = 0, selectedCount = 0) {
+    if (this.findEdge(source, target)) return;
+    this.edges.push({ source, target, weight, visitedCount, selectedCount });
+    this.layout();
   }
 
   updateNode(id, update) {
-    const node = this.graph.findNode(id);
+    const node = this.findNode(id);
     Object.assign(node, update);
-    this.render();
-  }
-
-  log(tracerKey) {
-    this.logData = tracerKey ? tracerManager.datas[tracerKey] : null;
-  }
-}
-
-class Graph {
-  constructor(nodes, edges, directed) {
-    this.nodes = nodes;
-    this.edges = edges;
-    this.directed = directed;
-  }
-
-  addNode(id, weight, visitedCount, x = 0, y = 0) {
-    if (this.findNode(id)) return;
-    this.nodes.push({ id, weight, visitedCount, x, y });
-  }
-
-  addEdge(source, target, weight, visitedCount) {
-    if (this.findEdge(source, target)) return;
-    this.edges.push({ source, target, weight, visitedCount });
   }
 
   findNode(id) {
     return this.nodes.find(node => node.id === id);
   }
 
-  findEdge(source, target, directed = this.directed) {
+  findEdge(source, target, directed = this.options.directed) {
     if (directed) {
       return this.edges.find(edge => edge.source === source && edge.target === target);
     } else {
@@ -132,7 +74,7 @@ class Graph {
     }
   }
 
-  findLinkedEdges(source, directed = this.directed) {
+  findLinkedEdges(source, directed = this.options.directed) {
     if (directed) {
       return this.edges.filter(edge => edge.source === source);
     } else {
@@ -140,17 +82,35 @@ class Graph {
     }
   }
 
-  findLinkedNodeIds(source, directed = this.directed) {
+  findLinkedNodeIds(source, directed = this.options.directed) {
     const edges = this.findLinkedEdges(source, directed);
     return edges.map(edge => edge.source === source ? edge.target : edge.source);
   }
 
-  findLinkedNodes(source, directed = this.directed) {
+  findLinkedNodes(source, directed = this.options.directed) {
     const ids = this.findLinkedNodeIds(source, directed);
     return ids.map(id => this.findNode(id));
   }
 
-  layoutCircle(rect) {
+  getRect() {
+    const { baseWidth, baseHeight, padding } = this.dimensions;
+    const left = -baseWidth / 2 + padding;
+    const top = -baseHeight / 2 + padding;
+    const right = baseWidth / 2 - padding;
+    const bottom = baseHeight / 2 - padding;
+    const width = right - left;
+    const height = bottom - top;
+    return { left, top, right, bottom, width, height };
+  }
+
+  layout() {
+    const { method, args } = this.callLayout;
+    method.apply(this, args);
+  }
+
+  layoutCircle() {
+    this.callLayout = { method: this.layoutCircle, args: arguments };
+    const rect = this.getRect();
     const unitAngle = 2 * Math.PI / this.nodes.length;
     let angle = -Math.PI / 2;
     for (const node of this.nodes) {
@@ -162,7 +122,17 @@ class Graph {
     }
   }
 
-  layoutTree(rect, root) {
+  layoutTree(root = 0, sorted = false) {
+    this.callLayout = { method: this.layoutTree, args: arguments };
+    const rect = this.getRect();
+
+    if (this.nodes.length === 1) {
+      const [node] = this.nodes;
+      node.x = (rect.left + rect.right) / 2;
+      node.y = (rect.top + rect.bottom) / 2;
+      return;
+    }
+
     let maxDepth = 0;
     const leafCounts = {};
     let marked = {};
@@ -188,6 +158,7 @@ class Graph {
       node.x = rect.left + (h + leafCounts[node.id] / 2) * hGap;
       node.y = rect.top + v * vGap;
       const linkedNodes = this.findLinkedNodes(node.id, false);
+      if (sorted) linkedNodes.sort((a, b) => a.id - b.id);
       for (const linkedNode of linkedNodes) {
         if (marked[linkedNode.id]) continue;
         recursivePosition(linkedNode, h, v + 1);
@@ -198,7 +169,9 @@ class Graph {
     recursivePosition(rootNode, 0, 0);
   }
 
-  layoutRandom(rect) {
+  layoutRandom() {
+    this.callLayout = { method: this.layoutRandom, args: arguments };
+    const rect = this.getRect();
     const placedNodes = [];
     for (const node of this.nodes) {
       do {
@@ -208,6 +181,47 @@ class Graph {
       placedNodes.push(node);
     }
   }
+
+  visit(target, source, weight) {
+    this.visitOrLeave(target, source, weight, true);
+  }
+
+  leave(target, source, weight) {
+    this.visitOrLeave(target, source, weight, false);
+  }
+
+  visitOrLeave(target, source, weight, visit) {
+    const edge = this.findEdge(source, target);
+    if (edge) edge.visitedCount += visit ? 1 : -1;
+    const node = this.findNode(target);
+    node.weight = weight;
+    node.visitedCount += visit ? 1 : -1;
+    if (this.logData) {
+      this.logData.print(visit ? (source || '') + ' -> ' + target : (source || '') + ' <- ' + target);
+    }
+  }
+
+  select(target, source) {
+    this.selectOrDeselect(target, source, true);
+  }
+
+  deselect(target, source) {
+    this.selectOrDeselect(target, source, false);
+  }
+
+  selectOrDeselect(target, source, select) {
+    const edge = this.findEdge(source, target);
+    if (edge) edge.selectedCount += select ? 1 : -1;
+    const node = this.findNode(target);
+    node.selectedCount += select ? 1 : -1;
+    if (this.logData) {
+      this.logData.print(select ? (source || '') + ' => ' + target : (source || '') + ' <= ' + target);
+    }
+  }
+
+  log(tracerKey) {
+    this.logData = tracerKey ? tracerManager.datas[tracerKey] : null;
+  }
 }
 
 export default GraphData;
\ No newline at end of file
diff --git a/src/frontend/core/datas/LogData.js b/src/frontend/core/datas/LogData.js
index 44d1f9ae16a0a2a457f398725d8b7ffed7629013..98bca09392e7f01145253f6476f8d7d5ce13291e 100644
--- a/src/frontend/core/datas/LogData.js
+++ b/src/frontend/core/datas/LogData.js
@@ -8,7 +8,6 @@ class LogData extends Data {
 
   print(message) {
     this.messages.push(message);
-    this.render();
   }
 }
 
diff --git a/src/frontend/core/renderers/GraphRenderer/index.jsx b/src/frontend/core/renderers/GraphRenderer/index.jsx
index 402c0eeee87a782a72a77f6fd2aef1249f6aace0..417bec7280f71a10882332edc995733d4dd3c5b7 100644
--- a/src/frontend/core/renderers/GraphRenderer/index.jsx
+++ b/src/frontend/core/renderers/GraphRenderer/index.jsx
@@ -14,15 +14,16 @@ class GraphRenderer extends Renderer {
   handleMouseDown(e) {
     super.handleMouseDown(e);
     const coords = this.computeCoords(e);
-    const { graph, dimensions } = this.props.data;
+    const { nodes, dimensions } = this.props.data;
     const { nodeRadius } = dimensions;
-    this.selectedNode = graph.nodes.find(node => distance(coords, node) <= nodeRadius);
+    this.selectedNode = nodes.find(node => distance(coords, node) <= nodeRadius);
   }
 
   handleMouseMove(e) {
     if (this.selectedNode) {
       const coords = this.computeCoords(e);
       this.props.data.updateNode(this.selectedNode.id, coords);
+      this.refresh();
     } else {
       super.handleMouseMove(e);
     }
@@ -38,7 +39,7 @@ class GraphRenderer extends Renderer {
   }
 
   renderData() {
-    const { graph, options, dimensions } = this.props.data;
+    const { nodes, edges, options, dimensions } = this.props.data;
     const { baseWidth, baseHeight, nodeRadius, arrowGap, nodeWeightGap, edgeWeightGap } = dimensions;
     const { directed, weighted } = options;
     const viewBox = [
@@ -53,15 +54,18 @@ class GraphRenderer extends Renderer {
           <marker id="markerArrow" markerWidth="4" markerHeight="4" refX="2" refY="2" orient="auto">
             <path d="M0,0 L0,4 L4,2 L0,0" className={styles.arrow} />
           </marker>
+          <marker id="markerArrowSelected" markerWidth="4" markerHeight="4" refX="2" refY="2" orient="auto">
+            <path d="M0,0 L0,4 L4,2 L0,0" className={classes(styles.arrow, styles.selected)} />
+          </marker>
           <marker id="markerArrowVisited" markerWidth="4" markerHeight="4" refX="2" refY="2" orient="auto">
             <path d="M0,0 L0,4 L4,2 L0,0" className={classes(styles.arrow, styles.visited)} />
           </marker>
         </defs>
         {
-          graph.edges.sort((a, b) => a.visitedCount - b.visitedCount).map(edge => {
-            const { source, target, weight, visitedCount } = edge;
-            const { x: sx, y: sy } = graph.findNode(source);
-            let { x: ex, y: ey } = graph.findNode(target);
+          edges.sort((a, b) => a.visitedCount - b.visitedCount).map(edge => {
+            const { source, target, weight, visitedCount, selectedCount } = edge;
+            const { x: sx, y: sy } = this.props.data.findNode(source);
+            let { x: ex, y: ey } = this.props.data.findNode(target);
             const mx = (sx + ex) / 2;
             const my = (sy + ey) / 2;
             const dx = ex - sx;
@@ -76,7 +80,7 @@ class GraphRenderer extends Renderer {
             }
 
             return (
-              <g className={classes(styles.edge, visitedCount && styles.visited)} key={`${source}-${target}`}>
+              <g className={classes(styles.edge, selectedCount && styles.selected, visitedCount && styles.visited)} key={`${source}-${target}`}>
                 <path d={`M${sx},${sy} L${ex},${ey}`} className={classes(styles.line, directed && styles.directed)} />
                 {
                   weighted &&
@@ -90,10 +94,10 @@ class GraphRenderer extends Renderer {
           })
         }
         {
-          graph.nodes.map(node => {
-            const { id, x, y, weight, visitedCount } = node;
+          nodes.map(node => {
+            const { id, x, y, weight, visitedCount, selectedCount } = node;
             return (
-              <g className={classes(styles.node, visitedCount && styles.visited)} key={id}
+              <g className={classes(styles.node, selectedCount && styles.selected, visitedCount && styles.visited)} key={id}
                  transform={`translate(${x},${y})`}>
                 <circle className={styles.circle} r={nodeRadius} />
                 <text className={styles.id}>{id}</text>
diff --git a/src/frontend/core/renderers/GraphRenderer/stylesheet.scss b/src/frontend/core/renderers/GraphRenderer/stylesheet.scss
index a4a2f901c1bd0baef2e772d02cb1bb31da7e2ca6..d4f2331c5a766e5e676f6a8fe7495ce52562290c 100644
--- a/src/frontend/core/renderers/GraphRenderer/stylesheet.scss
+++ b/src/frontend/core/renderers/GraphRenderer/stylesheet.scss
@@ -24,6 +24,13 @@
       text-anchor: left;
     }
 
+    &.selected {
+      .circle {
+        fill: $color-selected;
+        stroke: $color-selected;
+      }
+    }
+
     &.visited {
       .circle {
         fill: $color-notified;
@@ -48,6 +55,20 @@
       text-anchor: middle;
     }
 
+    &.selected {
+      .line {
+        stroke: $color-selected;
+
+        &.directed {
+          marker-end: url(#markerArrowSelected);
+        }
+      }
+
+      .weight {
+        fill: $color-selected;
+      }
+    }
+
     &.visited {
       .line {
         stroke: $color-notified;
@@ -66,6 +87,10 @@
   .arrow {
     fill: $color-font;
 
+    &.selected {
+      fill: $color-selected;
+    }
+
     &.visited {
       fill: $color-notified;
     }
diff --git a/src/frontend/core/renderers/Renderer/index.jsx b/src/frontend/core/renderers/Renderer/index.jsx
index 885062f48da3b54e34ff30687b40321ffd94884f..6ef937ee73eb2cb54b8e55162a6c5aeb69d906a6 100644
--- a/src/frontend/core/renderers/Renderer/index.jsx
+++ b/src/frontend/core/renderers/Renderer/index.jsx
@@ -54,12 +54,6 @@ class Renderer extends React.Component {
     data.setOnRender(null);
   }
 
-  handleDrag(dx, dy) {
-    this.centerX -= dx;
-    this.centerY -= dy;
-    this.refresh();
-  }
-
   handleMouseDown(e) {
     const { clientX, clientY } = e;
     this.lastX = clientX;
@@ -72,7 +66,9 @@ class Renderer extends React.Component {
     const { clientX, clientY } = e;
     const dx = clientX - this.lastX;
     const dy = clientY - this.lastY;
-    this.handleDrag(dx, dy);
+    this.centerX -= dx;
+    this.centerY -= dy;
+    this.refresh();
     this.lastX = clientX;
     this.lastY = clientY;
   }
diff --git a/src/frontend/core/tracerManager.jsx b/src/frontend/core/tracerManager.jsx
index 767ca53ef3517f7433cdd5ba657de8cbe068f6e3..afa5c24698a0694545d8b3012ec95752e05bd775 100644
--- a/src/frontend/core/tracerManager.jsx
+++ b/src/frontend/core/tracerManager.jsx
@@ -52,6 +52,7 @@ class TracerManager {
   }
 
   render() {
+    Object.values(this.datas).forEach(data => data.render());
     if (this.onRender) this.onRender(this.renderers);
   }
 
@@ -166,7 +167,7 @@ class TracerManager {
     }
   }
 
-  sandboxEval(code){
+  sandboxEval(code) {
     const require = moduleName => window.modules[moduleName]; // fake require
     eval(code);
   }
diff --git a/src/frontend/core/tracers/GraphTracer.js b/src/frontend/core/tracers/GraphTracer.js
index feda89223aee6a4ae48eabfe34cdf59bc1cfd96c..206020df5c78f9cb14c2a8259e225098723317c3 100644
--- a/src/frontend/core/tracers/GraphTracer.js
+++ b/src/frontend/core/tracers/GraphTracer.js
@@ -5,19 +5,18 @@ class GraphTracer extends Tracer {
     super(title, options);
 
     this.register(
+      'addNode',
+      'addEdge',
+      'layoutCircle',
+      'layoutTree',
+      'layoutRandom',
       'visit',
       'leave',
+      'select',
+      'deselect',
       'log',
     );
   }
 }
 
-GraphTracer.LAYOUT = {
-  CIRCLE: 'circle',
-  TREE: 'tree',
-  RANDOM: 'random',
-  NONE: 'none',
-  // FORCE_DIRECTED: 'force_directed',
-};
-
 export default GraphTracer;
\ No newline at end of file