#include "FastLED.h"
#define DATA_PIN    2
//#define CLK_PIN   4
#define LED_TYPE    WS2811
#define COLOR_ORDER GRB
#define NUM_LEDS    40
CRGB leds[NUM_LEDS];
#define BUTTON_LEAD  3
#define BRIGHTNESS          96
#define FRAMES_PER_SECOND  120

#define SPEED 50 //higher value is slower
int showMode;
//int pos = 0;
//int posDir = 1;
uint8_t gHue = 0; // rotating "base color" used by many of the patterns

void setup() {
  delay(3000); // 3 second delay for recovery
  Serial.begin(9600);
  // tell FastLED about the LED strip configuration
  FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  // set master brightness control
  FastLED.setBrightness(BRIGHTNESS);
  attachInterrupt(1, buttonListener, RISING);
}

void loop() {
  line();
  EVERY_N_MILLISECONDS( 10 ) {
    gHue++;  /* slowly cycle the "base color" through the rainbow*/
  }
}

void line() {
  Serial.print ("start showMode = ");
  Serial.println (showMode);
  if (showMode == false) {
    for (int pos = 0; pos <= NUM_LEDS - 1; pos++) {
      Serial.print (pos);
      Serial.print (" , ");
//      Serial.println (posDir);
      FastLED.clear();
      leds[pos] += CHSV(gHue, 255, 255); //Center
      if (pos < NUM_LEDS) {
        leds[pos + 1] += CHSV(gHue, 255, 100); /*Leading edge of dot will be dimmed*/
      }
      if (pos > 1) {
        leds[pos - 1] += CHSV(gHue, 255, 100); /*if pos is zero do not send a negetive number to (leds)*/
      }
      Serial.print ("cntup showMode = ");
      Serial.println (showMode);
      FastLED.show();
      FastLED.delay(SPEED);
    }
    for (int pos = NUM_LEDS - 1; pos > 0; pos--) {
      Serial.print (pos);
      Serial.print (" , ");
//      Serial.println (posDir);
      FastLED.clear();
      leds[pos] += CHSV(gHue, 255, 255); /*Center*/
      if (pos < NUM_LEDS) {
        leds[pos + 1] += CHSV(gHue, 255, 100); /*Leading edge of dot will be dimmed*/
      }
      if (pos > 1) {
        leds[pos - 1] += CHSV(gHue, 255, 100); /*if pos is zero do not send a negetive number to (leds)*/
      }
      Serial.print ("cntdn showMode = ");
      Serial.println (showMode);
      FastLED.show();
      FastLED.delay(SPEED);

    }
  }
  if (showMode == true) {
    wipe();
    Serial.println ("wipe");
  }

}

void wipe() {
  fadeToBlackBy(leds, NUM_LEDS, 15);
  FastLED.show();
}

/* monitor button press */
void buttonListener() {
  delay(20); /*Reccomend a hardware debounce to ensure flawless response*/
  if (digitalRead(3) == true) {
    showMode = !showMode;
    Serial.print ("Button Press showMode = ");
    Serial.println (showMode);
  }
}

<----------SERIAL MONITOR OUTPUT----->
start showMode = 0
0 , cntup showMode = 0
1 , cntup showMode = 0
2 , cntup showMode = 0
3 , cntup showMode = 0
4 , cntup showMode = 0
5 , cntup showMode = 0
6 , cntup showMode = 0
7 , cntup showMode = 0
8 , cntup showMode = 0
9 , cntup showMode = 0
10 , cntup showMode = 0
11 , cntup showMode = 0
12 , cntup showMode = 0
13 , cntup showMode = 0
14 , cntup showMode = 0
15 , cntup showMode = 0
16 , cntup showMode = 0
17 , cntup showMode = 0
18 , cntup showMode = 0
19 , cntup showMode = 0
20 , cntup showMode = 0
21 , cntup showMode = 0
22 , cntup showMode = 0
23 , cntup showMode = 0
24 , cntup showMode = 0
25 , cntup showMode = 0
26 , cntup showMode = 0
27 , cntup showMode = 0
28 , cntup showMode = 0
29 , cntup showMode = 0
30 , cntup showMode = 0
31 , cntup showMode = 0
32 , cntup showMode = 0
33 , cntup showMode = 0
34 , cntup showMode = 0
35 , cntup showMode = 0
36 , cntup showMode = 0
37 , cntup showMode = 0
38 , cntup showMode = 0
39 , cntup showMode = 40
39 , cntdn showMode = 80
38 , cntdn showMode = 80
37 , cntdn showMode = 80
36 , cntdn showMode = 80
35 , cntdn showMode = 80
34 , cntdn showMode = 80
33 , cntdn showMode = 80
32 , cntdn showMode = 80
31 , cntdn showMode = 80
30 , cntdn showMode = 80
29 , cntdn showMode = 80
28 , cntdn showMode = 80
27 , cntdn showMode = 80
26 , cntdn showMode = 80
25 , cntdn showMode = 80
24 , cntdn showMode = 80
23 , cntdn showMode = 80
22 , cntdn showMode = 80
21 , cntdn showMode = 80
20 , cntdn showMode = 80
19 , cntdn showMode = 80
18 , cntdn showMode = 80
17 , cntdn showMode = 80
16 , cntdn showMode = 80
15 , cntdn showMode = 80
14 , cntdn showMode = 80
13 , cntdn showMode = 80
12 , cntdn showMode = 80
11 , cntdn showMode = 80
10 , cntdn showMode = 80
9 , cntdn showMode = 80
8 , cntdn showMode = 80
7 , cntdn showMode = 80
6 , cntdn showMode = 80
5 , cntdn showMode = 80
4 , cntdn showMode = 80
3 , cntdn showMode = 80
2 , cntdn showMode = 80
1 , cntdn showMode = 80
start showMode = 80
start showMode = 80
start showMode = 80
start showMode = 80
start showMode = 80