Here the source :

```
// Fit text mode area and canvas
area.fitCanvas(scale,canvas,font);

// Center canvas in page
canvas.style.marginTop = window.innerHeight/2-canvas.height*scale/2 + 'px';
canvas.style.marginLeft = window.innerWidth/2-canvas.width*scale/2 + 'px';

// Init a variable to store render charCode to keep
let keep = [];

// Keep red hearts
keep.push(font.encoding.descrToDec({"name":'♥','FG':"Red",'BG':"Black"}));

// Keep red letters F,R,E,P,A,L,E,S,T,I,N,E
let free_palestine = "FREPALESTINE";
for (var j = 0; j < free_palestine.length; j++){
  keep.push(font.encoding.descrToDec({"name":free_palestine[j],'FG':"Red",'BG':"Black"}));
}

// Set 60 frames per second
fps = 60;

// Set charCode randomization chances
let rdmChance = 0.9;

// Declare animation frame process
animation = function(){

  // Declare area render (Cell process)
  area.render(

    // This options are defined in a init.js script
    render_options,

    // This function will be applied to every cell / character render, 'return' sendind character code to render
    function(){

      // Transform keeped hearts to top left FREE PALESTINE text
      if (keep.includes(dn[i]) && i == 0) return keep[1];
      if (keep.includes(dn[i]) && i == 1) return keep[2];
      if (keep.includes(dn[i]) && i == 2) return keep[3];
      if (keep.includes(dn[i]) && i == 3) return keep[3];
      if (keep.includes(dn[i]) && i == 10) return keep[4];
      if (keep.includes(dn[i]) && i == 11) return keep[5];
      if (keep.includes(dn[i]) && i == 12) return keep[6];
      if (keep.includes(dn[i]) && i == 13) return keep[7];
      if (keep.includes(dn[i]) && i == 14) return keep[8];
      if (keep.includes(dn[i]) && i == 15) return keep[9];
      if (keep.includes(dn[i]) && i == 16) return keep[10];
      if (keep.includes(dn[i]) && i == 17) return keep[11];
      if (keep.includes(dn[i]) && i == 18) return keep[12];
      
      // Keep desired charCodes and eventually randomize character if not
      if (keep.includes(dn[i]) || Math.random()<rdmChances) return dn[i];

      // Get a random character code
      let charCode = mf(mr()*font.length);
      
      // Check if random character is an heart
      let is_heart = charCode == font.encoding.descrToDec({"name":'♥'});

      // If random character is heart, accelerate radomization chances
      if (is_heart) found -= 1/(w*h);

      // If random character is heart, colorize it red
      return font.encoding.mode(charCode,{
        "FG": is_heart ? "Red" : "Bright Black"
      });
    }
  );
}
```