Code that seems to crash the forum:

#include <FastLED.h>

#define NUM_LEDS 48
#define buttonPin1 5
#define buttonPin2 3

CRGB leds[NUM_LEDS];

void setup() {
  FastLED.addLeds < NEOPIXEL, PB1 > (leds, NUM_LEDS);
  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);

}

void loop() {

  if (digitalRead(buttonPin1) == LOW) {

    CRGB pattern[] = {
      CRGB(255, 255, 255),
      CRGB(255, 255, 255),
      CRGB(255, 0, 0),
      CRGB(255, 0, 0),

    };
    size_t pattern_sz = sizeof(pattern) / sizeof( * pattern);

    // a 8.8 fixed point position (so 256 = 1.0, 512 = 2.0, 65535 = 255.996)
    static uint16_t basepos = 0;
    // a copy of basepos to be modified over the length of the strip
    uint16_t ledpos = basepos;
    for (uint8_t ledno = 0; ledno < NUM_LEDS; ledno++) {
      // find the integer and fractional parts for this LED 
      uint8_t intpos = ledpos >> 8;
      uint8_t fracpos = ledpos & 0xff;
      // select the two colours to be blended for this LED
      CRGB colA = pattern[intpos % pattern_sz];
      CRGB colB = pattern[(intpos + 1) % pattern_sz];
      // fade colA towards colB by the fractional position
      leds[ledno] = fadeTowardColor(colA, colB, fracpos);
      // move along the source pattern by some fraction of a pixel
      ledpos -= 128;
    }
    FastLED.show();
    delay(10);
    // move the base position by some fractional amount
    basepos += beatsin8(5, 1, 128);

  }

  if (digitalRead(buttonPin2) == LOW) {

    CRGB pattern[] = {
      CRGB(255, 255, 255),
      CRGB(255, 255, 255),
      CRGB(0, 0, 255),
      CRGB(0, 0, 255),

    };
    size_t pattern_sz = sizeof(pattern) / sizeof( * pattern);

    // a 8.8 fixed point position (so 256 = 1.0, 512 = 2.0, 65535 = 255.996)
    static uint16_t basepos = 0;
    // a copy of basepos to be modified over the length of the strip
    uint16_t ledpos = basepos;
    for (uint8_t ledno = 0; ledno < NUM_LEDS; ledno++) {
      // find the integer and fractional parts for this LED 
      uint8_t intpos = ledpos >> 8;
      uint8_t fracpos = ledpos & 0xff;
      // select the two colours to be blended for this LED
      CRGB colA = pattern[intpos % pattern_sz];
      CRGB colB = pattern[(intpos + 1) % pattern_sz];
      // fade colA towards colB by the fractional position
      leds[ledno] = fadeTowardColor(colA, colB, fracpos);
      // move along the source pattern by some fraction of a pixel
      ledpos -= 128;
    }
    FastLED.show();
    delay(10);
    // move the base position by some fractional amount
    basepos += beatsin8(5, 1, 128);
  }

  if (digitalRead(buttonPin1 == LOW) && (buttonPin2 == LOW)) {

    CRGB pattern[] = {
      CRGB(255, 255, 255),
      CRGB(255, 255, 255),
      CRGB(0, 255, 0),
      CRGB(0, 255, 0),

    };
    size_t pattern_sz = sizeof(pattern) / sizeof( * pattern);

    // a 8.8 fixed point position (so 256 = 1.0, 512 = 2.0, 65535 = 255.996)
    static uint16_t basepos = 0;
    // a copy of basepos to be modified over the length of the strip
    uint16_t ledpos = basepos;
    for (uint8_t ledno = 0; ledno < NUM_LEDS; ledno++) {
      // find the integer and fractional parts for this LED 
      uint8_t intpos = ledpos >> 8;
      uint8_t fracpos = ledpos & 0xff;
      // select the two colours to be blended for this LED
      CRGB colA = pattern[intpos % pattern_sz];
      CRGB colB = pattern[(intpos + 1) % pattern_sz];
      // fade colA towards colB by the fractional position
      leds[ledno] = fadeTowardColor(colA, colB, fracpos);
      // move along the source pattern by some fraction of a pixel
      ledpos -= 128;
    }
    FastLED.show();
    delay(10);
    // move the base position by some fractional amount
    basepos += beatsin8(5, 1, 128);
  }
}

// Mark Kriegsman's fadeTowardColor from:
//  https://gist.github.com/kriegsman/d0a5ed3c8f38c64adcb4837dafb6e690 

// Helper function that blends one uint8_t toward another by a given amount
void nblendU8TowardU8(uint8_t & cur,
  const uint8_t target, uint8_t amount) {
  if (cur == target) return;

  if (cur < target) {
    uint8_t delta = target - cur;
    delta = scale8_video(delta, amount);
    cur += delta;
  } else {
    uint8_t delta = cur - target;
    delta = scale8_video(delta, amount);
    cur -= delta;
  }
}

// Blend one CRGB color toward another CRGB color by a given amount.
// Blending is linear, and done in the RGB color space.
// This function modifies 'cur' in place.
CRGB fadeTowardColor(CRGB & cur,
  const CRGB & target, uint8_t amount) {
  nblendU8TowardU8(cur.red, target.red, amount);
  nblendU8TowardU8(cur.green, target.green, amount);
  nblendU8TowardU8(cur.blue, target.blue, amount);
  return cur;
}