int circleSize = 0;
int circleX = 100;
int circleY = 100;

void setup() {
  size(200,200);
}

void draw() {
  background(0);
  stroke(255);
  fill(175,0,0);
  ellipse(mouseX,mouseY,circleSize,circleSize);  //Circle follows mouse with size equal to variable
  
  circleSize = abs(mouseX-pmouseX)+10;  //Sets variable equal to mouse speed plus ten
}