added arduino, modified build

arduino/libraries/Adafruit_Circuit_Playground/examples/mega_demo/Demo.h

@@ -0,0 +1,27 @@
+#ifndef DEMO_H
+#define DEMO_H
+
+// Define each mode with the following interface for a loop and modePress
+// function that will be called during the main loop and if the mode button
+// was pressed respectively.  It's up to each mode implementation to fill
+// these in and add their logic.
+class Demo {
+public:
+  virtual ~Demo() {}
+
+  virtual void loop() = 0;
+  virtual void modePress() = 0;
+};
+
+// Linear interpolation function is handy for all the modes to use.
+float lerp(float x, float xmin, float xmax, float ymin, float ymax) {
+  if (x >= xmax) {
+    return ymax;
+  }
+  if (x <= xmin) {
+    return ymin;
+  }
+  return ymin + (ymax-ymin)*((x-xmin)/(xmax-xmin));
+}
+
+#endif