Move the mouse...
<img src="face.svg" id="face" style="position: fixed;"/>
<script>
var face_friction = 0.95;
var face_acc = 0.1;
var frame_time = 20;
var face_speed = 30;
var face = document.getElementById("face");
var x = 50;
var y = 50;
var vx = 0;
var vy = 0;
var mx = 50;
var my = 50;

document.onmousemove = function(evt) {
    mx = evt.pageX;
    my = evt.pageY;
};

function update() {
    var spd;
    vx += (mx - x) * face_acc;
    vy += (my - y) * face_acc;
    spd = Math.sqrt(vx*vx + vy*vy) / face_speed;
    if (spd > 1) {
        vx /= spd;
        vy /= spd;
    }
    vx *= face_friction;
    vy *= face_friction;
    x += vx;
    y += vy;
    face.style.left = (x - 25) + "px";
    face.style.top  = (y - 25) + "px";
    setTimeout(update, frame_time);
}

setTimeout(update, frame_time);
</script>