float x=50, y=50, t=3, s=2, m;
void draw() {
    background(0);
    m=mouseY;
    ellipse(x, y, 9, 9);
    t=x>95||x<10&&y<m+25&&y>m-25?-t:t;
    x=x<5?50:x;
    s=y>95||y<5?-s:s;
    x+=t;
    y+=s;
    rect(5, m-25, 5, 50);
}