Amend mistakes

source/main.cpp

@@ -143,7 +143,7 @@ private:
 
 Block::Block()
     : shape((Shape)UBIT.random(SHAPE_TYPES_COUNT)) // choose a random shape
-    , facing(NORTH) // for now, all shapes face North
+    , facing(RotationDirection::NORTH) // for now, all shapes face North
 {}
 
 MicroBitImage Block::image() const {
@@ -167,24 +167,30 @@ int main() {
     // Initialise the micro:bit runtime.
     UBIT.init();
     // draw first dot to indicate runtime system is initialised
-    UBIT.display.setPixelValue(0, 2, 255);
+    UBIT.display.image.setPixelValue(0, 2, 255);
     // seed the PRNG with the HRNG
     UBIT.seedRandom();
     // draw second dot to indicate PRNG has been seeded
-    UBIT.display.setPixelValue(2, 2, 255);
+    UBIT.display.image.setPixelValue(2, 2, 255);
     // ensure display is set to black and white mode
     UBIT.display.setDisplayMode(DISPLAY_MODE_BLACK_AND_WHITE);
     // draw third and final dot to indicate screen has been set up
-    UBIT.display.setPixelValue(4, 2, 1);
+    UBIT.display.image.setPixelValue(4, 2, 1);
 
     UBIT.display.scroll("BLOCKS!");
 
     // XXX: simple debug test to check my FLASH images were stored correctly
+    // a simple clocker to check frame rate
+    bool strober = false;
     while (true) {
         // display new random blocks each second
         Block block;
-        UBIT.display.print(block.image(), 1, 1);
+        UBIT.display.print(block.image(), 2, 2);
+        // display clocker
+        UBIT.display.image.setPixelValue(0, 0, strober);
         UBIT.sleep(1000); // 1000ms or 1s sleep
+        // invert the clocker
+        strober = !strober;
     }
 
     // TODO: potentially remove this call, if clarified that it is not required.