Added flash attribute. Implemented more OpCodes

Desktop/Form1.cs

@@ -14,6 +14,7 @@ namespace Desktop
         private Z80 _cpu = null!;
         private MemoryBus _memoryBus = null!;
         private IO_Bus _simpleIoBus = null!;
+        private int _ulaFrameCount = 0;
 
         // The 16 physical colors of the ZX Spectrum (ARGB format)
         private readonly int[] SpectrumColors = new int[]
@@ -71,6 +72,10 @@ namespace Desktop
         // Public so the Debugger's background thread can call it 50 times a second
         public void RenderScreen()
         {
+            _ulaFrameCount++;
+            // The Spectrum flashes every 16 frames. 
+            // This boolean flips between true and false every 16 frames.
+            bool invertFlashPhase = (_ulaFrameCount % 32) >= 16;
             int[] pixelData = new int[256 * 192];
 
             // Loop through the 6144 bytes of Pixel RAM
@@ -95,10 +100,18 @@ namespace Desktop
                 int ink = attr & 0x07;
                 int paper = (attr >> 3) & 0x07;
                 int brightOffset = (attr & 0x40) != 0 ? 8 : 0;
-
+                bool isFlashSet = (attr & 0x80) != 0;
                 int inkColor = SpectrumColors[ink + brightOffset];
                 int paperColor = SpectrumColors[paper + brightOffset];
 
+                if (isFlashSet && invertFlashPhase)
+                {
+                    // Swap the ink and paper colors for this character block!
+                    int temp = inkColor;
+                    inkColor = paperColor;
+                    paperColor = temp;
+                }
+
                 // Draw the 8 pixels
                 for (int bit = 0; bit < 8; bit++)
                 {