diff --git a/simulator.py b/simulator.py
index 31f154e..514d89c 100755
--- a/simulator.py
+++ b/simulator.py
@@ -60,6 +60,7 @@ class Simulator:
             with socket.SocketIO(self.s, 'r') as buffer:
                 try:
                     time.sleep(1e-5)
+                    self.simulate()
                     req = buffer.readline()
                     self.s.setblocking(True)
                     match req:
@@ -77,6 +78,9 @@ class Simulator:
                 except OSError:
                     pass
 
+    def simulate(self):
+        pass
+
     def realize(self):
         pass
 
@@ -100,13 +104,14 @@ class Douche:
         self.xs = []
         self.ys = []
         self.line, = self.ax.plot(self.xs, self.ys)#, color=self.cm)
-        plt.show()
 
     def add_point(self, x, y):
+        print(x, y)
         self.xs.append(x)
         self.ys.append(y)
         self.line.set_data(self.xs, self.ys)
         plt.draw()
+        plt.show()
 
 
 class NaiveSimulator(Simulator, Douche):
@@ -115,9 +120,9 @@ class NaiveSimulator(Simulator, Douche):
     time_step = 0
     last_update = 0.
 
-    J = [1., 1., 1.] # Moment of inertia vector times 1/R
-    f = [0., 0., 0.] # viscous friction coefficient
-    G = [1., 1., 1.] # Motor gain : Gamma = G * delta_w
+    J = np.array([1., 1., 1.]) # Moment of inertia vector times 1/R
+    f = np.array([0., 0., 0.]) # viscous friction coefficient
+    G = np.array([1., 1., 1.]) # Motor gain : Gamma = G * delta_w
     # FIXME: this is not very realistic, this looks like a model of
     # an asynchronous motor, not a stepper.
 
@@ -134,9 +139,9 @@ class NaiveSimulator(Simulator, Douche):
         lt = time.time()
         self.time_step = lt - self.last_update
         self.last_update = lt
-        gamma = G*(command_spd - spd)
+        gamma = self.G*(self.command_spd - self.speed)
 
-        self.speed += 1./J * (G - f*self.speed ) * self.time_step
+        self.speed += 1./self.J * (self.G - self.f*self.speed ) * self.time_step
         self.pos += self.speed * self.time_step
 
         self.steps = np.ceil(self.pos * np.array([self.X_STEPS_PER_MM,