Confused With OOP

I´m making my first steps with OOP so I´m still in the darkness.

I placed a MC instance called "clip" at coordinates 0,0.

then I wrote this code


ActionScript Code:
function Square(x, y) {    this._x = x;    this._y = y;}clip = new Square(200, 200);trace(clip._x);trace(clip._y);Square.prototype.moveTheClip = move;function move() {    this._x += 20;}button.onPress = function() {    clip.moveTheClip();};


Nothing is working here (especially my brain, I know).
Although the trace command returns 200,200 the clip is still in 0,0 and moveTheClip just moves nothing...