Add Simple Documentation

lib/service/configuration_service.dart

@@ -6,6 +6,12 @@ class ConfigurationService {
   bool showGrid;
 
   int _simSpeed;
+
+  /// Simulation Speed
+  ///
+  /// Sets the number of updates the simulation takes per second. Can range from
+  /// 1 to arbitrarily high numbers (though setting it too high can potentially
+  /// make the app brittle).
   int get simSpeed => _simSpeed;
   void set simSpeed(int val) {
     _simSpeed = val;

lib/src/Engine.dart

@@ -6,8 +6,19 @@ class Engine {
   // Elapsed Time Counter - useful for Safety Timeout
   Stopwatch _elapsed = new Stopwatch();
 
-  // Game Tick Rate - *does* impact game speed TODO add configurable option
+  /// Game Tick Rate
+  ///
+  /// *does* impact game speed; dictates how long each logic step takes. Only
+  /// interesting for engine internal calculations, to set simulation speed
+  /// from the outside use stepsPerSecond instead.
   int _MS_PER_STEP = 1000 ~/ 3;
+
+  /// Set Logic Updates per Second
+  ///
+  /// Dictates simulation speed. Sets the amount of (logic) updates per second.
+  /// Translations between number of updates and their timings is not exact so
+  /// comparing this variable to fixed ints might not yield the expected results.
+  /// Does not affect render frequency, which is handled by framesPerSecond.
   int get stepsPerSecond => 1000 ~/ _MS_PER_STEP;
   set stepsPerSecond(int val) => _MS_PER_STEP = 1000 ~/ val;