SCREEN OVER MOUSE THING:

var x = document.createElement("div");
x.style.position="fixed";
x.style.top='0';
x.style.backgroundColor="blue";
x.style.height="200px";
x.style.width="200px";
x.style.zIndex="99";
document.body.appendChild(x);
document.onmousemove = function(e){x.style.height=e.clientY+ "px"; x.style.width=e.clientX + "px";}




DIV FOLLOW MOUSE:
var x = document.createElement("div");
x.style.position="fixed";x.style.top="0";x.style.zIndex="99";x.style.backgroundColor="blue";x.style.width="50px";x.style.height="50px";
document.onmousemove=function(e){x.style.top=(e.clientY-25)+'px';x.style.left=(e.clientX-25)+'px'};document.documentElement.style.cursor="none";
document.body.appendChild(x);




PRANK: THE SPASTIC SMILEY:
var x = document.createElement("div");x.style.position="fixed";x.style.top="0";x.style.height="200px";x.style.width="200px";x.innerHTML=":D";x.style.fontSize="72px";x.style.transform="rotate(90deg)";x.style.backgroundColor="white";
document.onmousemove=function(e){var xm = Math.floor((Math.random()*250)+200); var ym = Math.floor((Math.random()*250)+200);x.style.height=ym+'px';x.style.width=xm+'px';x.style.top=e.clientY+'px';x.style.left=e.clientX+'px';x.style.transform="translate(-50%,-50%) rotate(90deg)";};
document.body.appendChild(x);


PRANK: THE SMILEY TAKEOVER:
var x = document.createElement("div");x.style.height=window.innerHeight+'px';x.style.width=window.innerWidth+'px';x.style.position="fixed";x.style.top="0";x.style.left="0";x.style.backgroundColor="white";x.style.display="flex";x.style.alignItems="center";x.style.justifyContent="center";x.style.zIndex="99"; var y = document.createElement("div");y.style.top="200px";y.style.width="200px";y.innerHTML=":D";y.style.fontSize="200px";document.onmousemove=function(e){if(e.clientX < (window.innerWidth/2)){y.style.transform="rotate(90deg)"} else {y.style.transform="rotate(90deg) scaleY(-1)"}};x.appendChild(y);document.body.appendChild(x);
x.style.opacity="0";var o = 0;var t = setInterval(function(){o+=0.01;x.style.opacity=o;y.style.opacity=o;if(x.style.opacity>=1){clearInterval(t);alert("hello!");document.documentElement.style.overflow="hidden";}},100);