add a ui with speed/play/pause/reset controls

UI.cs

@@ -0,0 +1,47 @@
+
+using UnityEngine;
+using UnityEngine.UI;
+
+public class UI : MonoBehaviour {
+
+    public Text generateButton;
+    public Text playButton;
+    public Text speed;
+    public Text step;
+
+    private void Update () {
+        speed.text = State.STEPS_PER_SECOND.ToString();
+        step.text = "Step: " + Simulation.CURRENT_STEP.ToString();
+    }
+
+    public void FasterButtonClicked () {
+        State.STEPS_PER_SECOND = Mathf.Clamp(++State.STEPS_PER_SECOND, 1, 30);
+    }
+
+    public void GenerateButtonClicked () {
+        generateButton.text = "Generate";
+        playButton.text = "Play";
+        State.PAUSED = true;
+        Simulation.Init();
+        Simulation.Render();
+    }
+
+    public void PlayButtonClicked () {
+        generateButton.text = "Reset";
+        if ( State.PAUSED ) {
+            State.PAUSED = false;
+            playButton.text = "Pause";
+            State.DELTA_TIME = 0;
+            Simulation.Step();
+            Simulation.Render();
+        } else {
+            State.PAUSED = true;
+            playButton.text = "Play";
+        }
+    }
+
+    public void SlowerButtonClicked () {
+        State.STEPS_PER_SECOND = Mathf.Clamp(--State.STEPS_PER_SECOND, 1, 30);
+    }
+
+}