Emanuele Feronato

var game;
var gridWidth = 40;
var gridHeight = 40;
var tileSize = 16;

window.onload = function() {	
	game = new Phaser.Game(640, 640, Phaser.AUTO, "");
     game.state.add("PlayGame", playGame);
     game.state.start("PlayGame");
}

var playGame = function(game){};

playGame.prototype = {
     preload: function(){
           game.load.image("tile", "tile.png");
     },
     create: function(){
          var startCol = game.rnd.between(0, gridWidth - 1);
          var startRow = game.rnd.between(0, gridHeight - 1);
          this.startPoint = game.add.sprite(startCol * tileSize, startRow * tileSize, "tile");
          this.startPoint.inputEnabled = true;
          this.startPoint.input.enableDrag();
          this.startPoint.input.boundsRect = new Phaser.Rectangle(0, 0, game.width, game.height);
          this.startPoint.input.enableSnap(tileSize, tileSize, true, true);
          do{
               var endCol = game.rnd.between(0, gridWidth - 1);
               var endRow = game.rnd.between(0, gridHeight - 1);     
          } while (startRow == endRow && startCol == endCol);
          this.endPoint = game.add.sprite(endCol * tileSize, endRow * tileSize, "tile");
          this.endPoint.inputEnabled = true;
          this.endPoint.input.enableDrag();
          this.endPoint.input.boundsRect = new Phaser.Rectangle(0, 0, game.width, game.height);
          this.endPoint.input.enableSnap(tileSize, tileSize, true, true);
          this.lineGroup = game.add.group();
          this.lineGraphics = game.add.graphics(0, 0);
     },
     update: function(){
          this.lineGroup.removeAll(true);
          this.lineGraphics.clear();
          this.lineGraphics.lineStyle(3, 0x00ff00);
          this.lineGraphics.moveTo(this.startPoint.x + tileSize / 2, this.startPoint.y + tileSize / 2);
          this.lineGraphics.lineTo(this.endPoint.x + tileSize / 2, this.endPoint.y + tileSize / 2);
          var x0 = this.startPoint.x / tileSize;
          var x1 = this.endPoint.x / tileSize;
          var y0 = this.startPoint.y / tileSize;
          var y1 = this.endPoint.y / tileSize;
          var dx = Math.abs(x1 - x0);
          var sx = -1;
          if(x0 < x1){
               var sx = 1
          }
          var dy = Math.abs(y1 - y0);
          var sy = -1;
          if(y0 < y1){
               var sy = 1;
          }
          var err = -dy / 2;
          if(dx > dy){
               err = dx / 2;
          }
          do{
               var tile = game.add.sprite(x0 * tileSize, y0 * tileSize, "tile");
               tile.alpha = 0.5;
               this.lineGroup.add(tile);
               var e2 = err;
               if(e2 > -dx){
                    err -= dy;
                    x0 += sx;
               }
               if(e2 < dy){
                    err += dx;
                    y0 += sy;
               }
          } while(x0 != x1 || y0 != y1)   
     }
}