Update BlinkWithoutDelay.ino example

* Remove unused ledPin constant
* Make comments more natural language
* Change if/ese statement to demonstrate shorthand variable flipping

Author: codetheorist

examples/02.Digital/BlinkWithoutDelay/BlinkWithoutDelay.ino

@@ -22,50 +22,45 @@
   by Scott Fitzgerald
   modified 9 Jan 2017
   by Arturo Guadalupi
+  modified 18 Feb 2018
+  by Alex Scott
 
   This example code is in the public domain.
 
   http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
 */
 
-// constants won't change. Used here to set a pin number:
-const int ledPin =  LED_BUILTIN;// the number of the LED pin
+// Unchangeable constant to hold our blink interval in milliseconds:
+const long interval = 1000;
 
-// Variables will change:
-int ledState = LOW;             // ledState used to set the LED
+// Setup a variable to hold our LED state
+int ledState = LOW;
 
 // Generally, you should use "unsigned long" for variables that hold time
 // The value will quickly become too large for an int to store
 unsigned long previousMillis = 0;        // will store last time LED was updated
 
-// constants won't change:
-const long interval = 1000;           // interval at which to blink (milliseconds)
-
 void setup() {
-  // set the digital pin as output:
-  pinMode(ledPin, OUTPUT);
+  // Set the digital pin as output:
+  pinMode(LED_BUILTIN, OUTPUT);
 }
 
 void loop() {
-  // here is where you'd put code that needs to be running all the time.
+  // This is where you'd put code that needs to be running all the time.
 
-  // check to see if it's time to blink the LED; that is, if the difference
-  // between the current time and last time you blinked the LED is bigger than
+  // Check to see if it's time to blink the LED; that is, if the difference
+  // between the current time and last time you blinked the LED is greater than
   // the interval at which you want to blink the LED.
   unsigned long currentMillis = millis();
 
   if (currentMillis - previousMillis >= interval) {
-    // save the last time you blinked the LED
+    // Save the last time you blinked the LED
     previousMillis = currentMillis;
 
-    // if the LED is off turn it on and vice-versa:
-    if (ledState == LOW) {
-      ledState = HIGH;
-    } else {
-      ledState = LOW;
-    }
+    // Inverse the state of our LED pin:
+    ledState = !ledState;
 
-    // set the LED with the ledState of the variable:
-    digitalWrite(ledPin, ledState);
+    // Set the LED with the updated LED state:
+    digitalWrite(LED_BUILTIN, ledState);
   }
 }