Implementing Timer and its examples

lib/time.dart

@@ -1,19 +1,36 @@
 
+/// Simple utility class that helps handling time counting and implementing interval like events.
+///
 class Timer {
   final double _limit;
   void Function() _callback;
-  double _current;
+  bool _repeat;
+  double _current = 0;
   bool _running = false;
 
-  Timer(this._limit, this._callback);
+  Timer(this._limit, { repeat = false, callback }) {
+    _repeat = repeat;
+    _callback = callback;
+  }
+
+  double get current {
+    return _current;
+  }
 
   void update(double dt) {
     if (_running) {
       _current += dt;
 
       if (isFinished()) {
-        _running = false;
-        _callback();
+        if (_repeat) {
+          _current -= _limit;
+        } else {
+          _running = false;
+        }
+
+        if (_callback != null) {
+          _callback();
+        }
       }
     }
   }
@@ -26,7 +43,7 @@ class Timer {
     _current = 0;
     _running = true;
   }
-
+  
   void stop() {
     _current = 0;
     _running = false;