[iNils]

Самый простой способ, это в двухмерном массиве менять индексы при движении, а потом сравнивать этот массив с "правильным"

this.lineStyle (0, 0, 0);
this.beginFill (0x666666);
this.moveTo (10, 10);
this.lineTo (140, 10);
this.lineTo (140, 140);
this.lineTo (10, 140);
this.lineTo (10, 10);
this.endFill ();
/*******************************************************************/
f = new TextFormat ("Verdana", 13, 0xFF6600, true);
f.align = "center";
/*******************************************************************/
init = function () {
	a = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 0]];
	v = [[0,-1],[0,1],[-1,0],[1,0]]
	x = 3;
	y = 3;
	for (p = 1; p < 200;){
		r = random (4);
		i = x + v[r][0];
		j = y + v[r][1];
		if (a[i][j] and a[i][j]!= o) {
			o = a[i][j];
			a[i][j] = a[x][y];
			a[x][y] = o;
			x = i;
			y = j;
			p++;
		}
	}
	v = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 0]];
	p = [[],[],[],[]];
	for (i = 0; i < 4; i++) {
		for (j = 0; j < 4; j++) {
			p[i][j] = a[i][j];
			if (a[i][j] != 0) {
				createEmptyMovieClip ("m" + p[i][j], p[i][j]);
				this["m" + p[i][j]].lineStyle (0, 0, 0);
				this["m" + p[i][j]].beginFill (0x333333);
				this["m" + p[i][j]].lineTo (30, 0);
				this["m" + p[i][j]].lineTo (30, 30);
				this["m" + p[i][j]].lineTo (0, 30);
				this["m" + p[i][j]].lineTo (0, 0);
				this["m" + p[i][j]].endFill ();
				this["m" + p[i][j]].createTextField ("t", 0, 0, 3, 30, 30);
				this["m" + p[i][j]].t.setNewTextFormat (f);
				this["m" + p[i][j]].t.text = p[i][j];
				this["m" + p[i][j]].i = i;
				this["m" + p[i][j]].j = j;
				this["m" + p[i][j]]._y = i * 32 + 12;
				this["m" + p[i][j]]._x = j * 32 + 12;
				this["m" + p[i][j]].onRelease = function () {
					if (p[this.i][this.j - 1] == 0) {
						this._x -= 32;
						o = p[this.i][this.j - 1];
						p[this.i][this.j - 1] = p[this.i][this.j];
						p[this.i][this.j] = o;
						this.j--;
					} else if (p[this.i][this.j + 1] == 0) {
						this._x += 32;
						o = p[this.i][this.j + 1];
						p[this.i][this.j + 1] = p[this.i][this.j];
						p[this.i][this.j] = o;
						this.j++;
					} else if (p[this.i - 1][this.j] == 0) {
						this._y -= 32;
						o = p[this.i - 1][this.j];
						p[this.i - 1][this.j] = p[this.i][this.j];
						p[this.i][this.j] = o;
						this.i--;
					} else if (p[this.i + 1][this.j] == 0) {
						this._y += 32;
						o = p[this.i + 1][this.j];
						p[this.i + 1][this.j] = p[this.i][this.j];
						p[this.i][this.j] = o;
						this.i++;
					}
					if (p.toString () == v.toString ()) {
						for (i = 0; i < 16; i++) {
							_root["m" + i].removeMovieClip ();
						}
						_root.createTextField ("t", 100, 0, 60, 150, 25);
						_root.t.setNewTextFormat (f);
						_root.t.selectable = false;
						_root.t.text = "WIN";
						_root.onMouseUp = function () {
							delete _root.onMouseUp;
							_root.init ();
						};
					}
				}
			}
		}
	}
};
init ();

Синим отмечена проверка