diff --git a/Arduino/LEDstream/LEDstream.pde b/Arduino/LEDstream/LEDstream.pde
index de1dafd..3067f39 100644
--- a/Arduino/LEDstream/LEDstream.pde
+++ b/Arduino/LEDstream/LEDstream.pde
@@ -83,7 +83,7 @@ void setup()
   unsigned long
     t             = 0;
 
-  LED_DDR  |= LED_PIN;  // Enable output for LED
+  LED_DDR  |=  LED_PIN; // Enable output for LED
   LED_PORT &= ~LED_PIN; // LED off
 
   Serial.begin(115200); // Teensy/32u4 disregards baud rate; is OK!
@@ -99,6 +99,22 @@ void setup()
   // SPI clock line only.  Your mileage may vary.  Experiment!
   // SPI.setClockDivider(SPI_CLOCK_DIV4);  // 4 MHz
 
+  // Issue test pattern to LEDs on startup.  This helps verify that
+  // wiring between the Arduino and LEDs is correct.  Not knowing the
+  // actual number of LEDs connected, this sets all of them (well, up
+  // to the first 25,000, so as not to be TOO time consuming) to red,
+  // green, blue, then off.  Once you're confident everything is working
+  // end-to-end, it's OK to comment this out and reprogram the Arduino.
+  uint8_t testcolor[] = { 0, 0, 0, 255, 0, 0 };
+  for(char n=3; n>=0; n--) {
+    for(c=0; c<25000; c++) {
+      for(i=0; i<3; i++) {
+        for(SPDR = testcolor[n + i]; !(SPSR & _BV(SPIF)); );
+      }
+    }
+    delay(1); // One millisecond pause = latch
+  }
+
   // loop() is avoided as even that small bit of function overhead
   // has a measurable impact on this code's overall throughput.
 
diff --git a/Processing/Adalight/Adalight.pde b/Processing/Adalight/Adalight.pde
index d69c30b..5fcb3af 100644
--- a/Processing/Adalight/Adalight.pde
+++ b/Processing/Adalight/Adalight.pde
@@ -36,6 +36,7 @@ GraphicsDevice[] gs;
 PImage           preview = createImage(arrayWidth, arrayHeight, RGB);
 Rectangle        bounds;
 Serial           port;
+DisposeHandler   dh; // For disabling LEDs on exit
 
 void setup() {
   GraphicsEnvironment ge;
@@ -43,6 +44,7 @@ void setup() {
   int                 i;
   float               f;
 
+  dh   = new DisposeHandler(this);
   port = new Serial(this, Serial.list()[0], 115200);
 
   size(arrayWidth * imgScale, arrayHeight * imgScale, JAVA2D);
@@ -151,3 +153,20 @@ color block(PImage image, int x, int y) {
   return color(r / s2, g / s2, b / s2);
 }
 
+// The DisposeHandler is called on program exit (but before the Serial
+// library is shutdown), in order to turn off the LEDs (reportedly more
+// reliable than stop()).  Seems to work for the window close box and
+// escape key exit, but not the 'Quit' menu option.
+// Thanks to phi.lho in the Processing forums.
+
+public class DisposeHandler {
+  DisposeHandler(PApplet pa) {
+    pa.registerDispose(this);
+  }
+  public void dispose() {
+    // Fill buffer (after header) with 0's, and issue to Arduino...
+    Arrays.fill(buffer, 6, buffer.length, byte(0));
+    port.write(buffer);
+  }
+}
+