// https://forum.makerforums.info/t/2-dimensional-blur-this-video-shows-the-new-blur2d-capability-newly-available-on-the-fastled/64648
// https://gist.github.com/kriegsman/5adca44e14ad025e6d3b

#include <FastLED.h>

const uint8_t kMatrixWidth  = 16;
const uint8_t kMatrixHeight = 16;
const uint8_t kBorderWidth = 1;

#define NUM_LEDS    (kMatrixWidth*kMatrixHeight)
CRGB leds[NUM_LEDS];

// Color correction for the SmartMatrix
#define COLOR_CORRECTION CRGB(255,110,178)

void setup()
{
  // Serial.begin(115200);
  FastLED.addLeds<NEOPIXEL, 3>(leds, NUM_LEDS).setCorrection(COLOR_CORRECTION);
}

void loop()
{
  static uint8_t counter = 0 ;
  // 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.
  if( counter % 3 == 0 ) {
    uint8_t blurAmount = beatsin8(2, 100, 150);
    blur2d( leds, kMatrixWidth, kMatrixHeight, blurAmount);
    // Serial.println(blurAmount);
  }
  counter++;

  // Use two out-of-sync sine waves
  uint8_t  i = beatsin8( 27, kBorderWidth, kMatrixHeight - kBorderWidth);
  uint8_t  j = beatsin8( 41, kBorderWidth, kMatrixWidth - kBorderWidth);

  // Also calculate some reflections
  uint8_t ni = (kMatrixWidth - 1) - i;
  uint8_t nj = (kMatrixWidth - 1) - j;

  // The color of each point shifts over time, each at a different speed.
  uint16_t ms = millis();
  leds[XY( i, j)] += CHSV( ms / 11, 255, 255);
  leds[XY( j, i)] += CHSV( ms / 13, 255, 255);
  leds[XY(ni, nj)] += CHSV( ms / 17, 255, 255);
  leds[XY(nj, ni)] += CHSV( ms / 29, 255, 255);
  leds[XY( i, nj)] += CHSV( ms / 37, 255, 255);
  leds[XY(ni, j)] += CHSV( ms / 41, 255, 255);

  FastLED.show();
}

uint16_t XY(uint8_t x, uint8_t y) {
  if (x >= kMatrixWidth) return NUM_LEDS;
  if (y >= kMatrixHeight) return NUM_LEDS;
  return y * kMatrixWidth + x;
}