Держи такое начало, остальное
самсама прикрутишь
<body style="width: 100%; height: 100%;">
<div style="position: absolute; left: 0; top: 0; width: 10px; height: 10px; background: green; border-radius: 5"></div>
X: <input><br>
Y: <input>
<script>
window.onload = function () {
var elems = document.body.children;
var point = elems[0]
var fieldX = elems[1];
var fieldY = elems[3];
fieldX.onkeyup = function () {
point.style.left = this.value + 'px';
}
fieldY.onkeyup = function () {
point.style.top = this.value + 'px';
}
}
</script>
