FastLED 3.1 2-D blur demo on 8x8 matrix

SquareSwirl.ino

#include <FastLED.h>

#define LED_PIN  6
#define LED_TYPE WS2811
#define COLOR_ORDER GRB

const uint8_t kSquareWidth = 8;
const uint8_t kBorderWidth = 1;

#define NUM_LEDS    (kSquareWidth*kSquareWidth)
CRGB leds[NUM_LEDS];

void setup() 
{
  FastLED.addLeds<LED_TYPE,LED_PIN,COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
}

void loop()
{
  // Apply some blurring to whatever's already on the matrix
  // Note that we never actually clear the matrix, we just constantly
  // blur it repeatedly.  Since the blurring is 'lossy', there's
  // an automatic trend toward black -- by design.
  uint8_t blurAmount = dim8_raw( beatsin8(3,64,192) );
  blur2d( leds, kSquareWidth, kSquareWidth, blurAmount);

  // Use two out-of-sync sine waves
  uint8_t  i = beatsin8(  91, kBorderWidth, kSquareWidth-kBorderWidth);
  uint8_t  j = beatsin8( 109, kBorderWidth, kSquareWidth-kBorderWidth);
  uint8_t  k = beatsin8(  73, kBorderWidth, kSquareWidth-kBorderWidth);
  
  // The color of each point shifts over time, each at a different speed.
  uint16_t ms = millis();  
  leds[XY( i, j)] += CHSV( ms / 29, 200, 255);
  leds[XY( j, k)] += CHSV( ms / 41, 200, 255);
  leds[XY( k, i)] += CHSV( ms / 73, 200, 255);
  
  FastLED.show();
}

// Trivial XY function for the 8x8 grid; use a different XY 
// function for different matrix grids.  See XYMatrix example for code.
uint16_t XY( uint8_t x, uint8_t y) { return (y * kSquareWidth) + x; }

I added the serpentine XY routine and it looks awesome.