diff --git a/gamedata.cpp b/gamedata.cpp
index 4c084d9..1e2c074 100644
--- a/gamedata.cpp
+++ b/gamedata.cpp
@@ -101,6 +101,16 @@ void GameData::handle_click(int x, int y)
 	if (current == NULL) return;
 	int dist = MathUtils::distance(current->x, current->y, current->z,
 				       x, y, 0);
+
+	Vertex* temp = new Vertex(x, y, 0, NODE_RADIUS);
+	if (crosses_edge(current, temp) ||
+	    vertex_would_overlap(x, y, 0, NODE_RADIUS))
+	{
+	    delete temp;
+	    return;
+	}
+	delete temp;
+
 	if (dist <= get_range())
 	{
 	    if (turn->spend_energy(dist))
diff --git a/graph.h b/graph.h
index 6755451..d1de18f 100644
--- a/graph.h
+++ b/graph.h
@@ -42,10 +42,10 @@ class Graph
 
  protected:
     list<Vertex*> vertices;
+    bool crosses_edge(Vertex* a, Vertex* b);
+    bool vertex_would_overlap(int x, int y, int z, int r);
 
  private:
-    bool vertex_would_overlap(int x, int y, int z, int r);
-    bool crosses_edge(Vertex* a, Vertex* b);
     bool planar;
 };