added arduino, modified build

arduino/libraries/Adafruit_Circuit_Playground/examples/FidgetSpinner/FidgetSpinner.h

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+// Fidget spinner logic.
+// This class represents a fidget spinner that can be spun to a specified
+// velocity and then over time will slow down and stop.  The spinner keeps track
+// of its continuous (floating point) position value within the range 0...<10
+// so it can map to CircuitPlayground pixel positions easily.// Author: Tony DiCola
+// License: MIT License (https://opensource.org/licenses/MIT)
+// Usage:
+// - Create an instance of the class (specifying a custom decay value between 0 and 1,
+//   the lower the decay the faster the spinner slows down).
+// - Call spin to start the spinner moving at the specified velocity (in pixels/second).
+// - Call getPosition periodically to get the current spinner position given an elapsed
+//   amount of seconds since the last getPosition call.
+#ifndef FIDGETANIMATION_H
+#define FIDGETANIMATION_H
+
+class FidgetSpinner {
+public:
+  FidgetSpinner(float decay=0.5):
+    _position(0.0), _velocity(0.0), _elapsedS(0.0), _decay(decay)
+  {}
+
+  void spin(float velocity) {
+    // Start the fidget spinner moving at the specified velocity (in pixels/second).
+    // Over time the spinner will slow down based on its decay value.
+    _velocity = velocity;
+    _elapsedS = 0.0;  // Reset elapsed time to start the decay from the beginning.
+  }
+
+  float getPosition(float deltaS) {
+    // Get the fidget spinner's current position after moving for the specified number
+    // of milliseconds.  Returns a continuous value in the range 0...<10.
+    _elapsedS += deltaS;
+    // Compute current velocity based on exponential decay of initial
+    // velocity over the elapsed time (this causes the spinner to
+    // gradually slow down and mimics the effects of friction).
+    float currentVelocity = _velocity*pow(_decay, _elapsedS);
+    // Now move the position based on the current velocity.
+    _position += currentVelocity*deltaS;
+    // Finally make sure position is constrained within 0...<10 range.
+    _position = fmod(_position, 10.0);
+    if (_position < 0.0) {
+      // Ensure position is never negative by wrapping back to the
+      // same pixel position in a positive location.
+      _position += 10.0;
+    }
+    return _position;
+  }
+
+private:
+  float _position;
+  float _velocity;
+  float _elapsedS;
+  float _decay;
+};
+
+#endif