For loop matrix index

[glv]

@niuuin

This is my attempt, for (int i = sq(total); i >= 0; i --) {} is there something wrong with my calculation method?

See error:

sq() returns a float:
https://processing.org/reference/sq_.html

Try:
total*total which returns an int

Or this to convert the float to an int:
https://processing.org/reference/intconvert_.html

The i -- seemed to work once I corrected code but really should be i-- without spaces.

@niuuin

How do I achieve the flashback effect in the schematic, please?

Consider this:

int t, total;
float itemSize;

void setup() 
  {
  size(800, 800); 
  //pixelDensity(2);
  smooth();
  rectMode(CENTER);

  total = 4;
  t = 4;
  itemSize = width/total;
  }

void draw() 
  {
  for (int i = 0; i < sq(total); i ++) 
    {
    float x = i % total * itemSize + itemSize/2;
    float y = i / total * itemSize + itemSize/2;
    fill(-1);
    square(x, y, itemSize * 0.8);

    textAlign(CENTER, CENTER);
    textSize(24);

    fill(0);
    text((i/t)%2, x, y-60);
    text(i%t, x, y-30);
    text(i, x, y);
    text(i/t, x, y+30);
    text(t-i%t, x, y+60); 
    }
  }

Output from above:

From the above I was able to do some math and achieve this:

An if\else statement was used to determine odd\even lines and print the correct order.

I took advantage of integer math in my example above.

:)