Extended MatrixEffect to also get RainbowMatrixEffect and RandomMatrixEffect.

Side note: You know you understand C++ when you understand the meaning 
and reason for "MatrixEffect** _columns". ;-)

include/effect_matrix.h

@@ -1,5 +1,4 @@
-#ifndef effect_matrix_H
-#define effect_matrix_H
+#pragma once
 
 #include "prototypes.h"
 #include "Effect.h"
@@ -8,10 +7,12 @@
 #include "my_color_palettes.h"
 
 class MatrixEffectColumn {
-private:
-    int x, y;
-    int length;
+protected:
     Window* window;
+    int x, y;
+    int length = 1;
+    virtual CRGB _getColor(uint8_t height);
+private:
     uint16_t speed;
     boolean running;
     unsigned long last_move = 0;
@@ -19,24 +20,47 @@ public:
     MatrixEffectColumn();
     MatrixEffectColumn(Window* win, int xPos);
 
-    void start();
-
+    virtual void start();
     void advance();
-
     void draw();
-
     void loop();
 };
 
+class RainbowMatrixEffectColumn : public MatrixEffectColumn {
+protected:
+    CRGB _getColor(uint8_t height) override;
+public:
+    RainbowMatrixEffectColumn() : MatrixEffectColumn() {};
+    RainbowMatrixEffectColumn(Window* win, int xPos) : MatrixEffectColumn(win, xPos) {};
+};
+
+class RandomMatrixEffectColumn : public MatrixEffectColumn {
+protected:
+    uint8_t _hue = 42;
+    CRGB _getColor(uint8_t height) override;
+public:
+    void start() override;
+    RandomMatrixEffectColumn() : MatrixEffectColumn() {};
+    RandomMatrixEffectColumn(Window* win, int xPos) : MatrixEffectColumn(win, xPos) {};
+};
+
 class MatrixEffect : public Effect {
-private:
-    MatrixEffectColumn* _columns;
+protected:
+    MatrixEffectColumn** _columns;
 public:
     boolean can_be_shown_with_clock();
-    void start();
+    virtual void start();
     void stop();
     MatrixEffect();
     void loop();
 };
 
-#endif
+class RainbowMatrixEffect : public MatrixEffect {
+public:
+    void start() override;
+};
+
+class RandomMatrixEffect : public MatrixEffect {
+public:
+    void start() override;
+};