Bounce

[mario_hater]

i have this code, it controls the player and when the player hits the wall, they are supposed to bounce off it. However it is possible to go through the wall if you go close to the wall, turn around and go forward, it drags you through the wall. here is the code:

speed = 0;
xspeed = 0;
yspeed = 0;
onEnterFrame = function () {
    player._x += xspeed;
    player._y -= yspeed;
    xspeed = Math.sin(Math.PI/180*player._rotation)*speed;
    yspeed = Math.cos(Math.PI/180*player._rotation)*speed;
    if (Key.isDown(Key.LEFT)) {
        player._rotation -= 10;
    }
    if (Key.isDown(Key.RIGHT)) {
        player._rotation += 10;
    }
    if (Key.isDown(Key.UP)) {
        if (speed<20) {
            speed += 2;
        }
    }
    if (speed>0) {
        speed -= 1;
    }
    if (speed<0) {
        speed += 1;
    }
    if (wall.hitTest(player._x, player._y, true)) {
        speed *= -1;
        xspeed *= -1;
        yspeed *= -1;
    }
};

does anyone know how to fix this?