color[] tiles;

int tileSize = 32;
int tileCount = 256 / tileSize;

int selectedTile = -1;
float t;

void setup()
{
  size(260, 260);
  
  tiles = new color[tileCount * tileCount];
  for (int i = 0; i < tileCount * tileCount; i++)
  {
    tiles[i] = color(random(255), random(255), random(255));
  }
  
  framerate(30);
}

void draw()
{
  if (selectedTile != -1)
  {
    color selectedColor = tiles[selectedTile];
    
    int selectedX = selectedTile % tileCount;
    int selectedY = selectedTile / tileCount;
    
    for (int y = 0; y < tileCount; y++)
    {
      for (int x = 0; x < tileCount; x++)
      {
        int xDistance = x - selectedX;
        int yDistance = y - selectedY;
        int distance = (int)sqrt(xDistance * xDistance + yDistance * yDistance);
        
        float factor = constrain(t - distance, 0, 1);
        factor = factor / 20;
        
        int each = y * tileCount + x;
        color eachColor = tiles[each];
        
        int mixRed = (int)min(255, red(selectedColor) * factor + red(eachColor) * (1 - factor));
        int mixGreen = (int)min(255, green(selectedColor) * factor + green(eachColor) * (1 - factor));
        int mixBlue = (int)min(255, blue(selectedColor) * factor + blue(eachColor) * (1 - factor));
        
        tiles[each] = color(mixRed, mixGreen, mixBlue);
      }
    }
  }
  
  background(255);
  
  for (int y = 0; y < tileCount; y++)
  {
    for (int x = 0; x < tileCount; x++)
    {
      noStroke();
      fill(tiles[y * tileCount + x]);
      rect(x * 32 + 4, y * tileSize + 4, 28, 28);
    }
  }
  
  t = t + 0.03;
}

void mousePressed()
{
  int mouseXWithoutBorder = mouseX - 2;
  int mouseYWithoutBorder = mouseY - 2;
  
  int tileX = mouseXWithoutBorder / tileSize;
  int tileY = mouseYWithoutBorder / tileSize;
  
  tileX = (int)constrain(tileX, 0, tileCount - 1);
  tileY = (int)constrain(tileY, 0, tileCount - 1);
  
  selectedTile = tileY * tileCount + tileX;
  
  t = 1;
}