function drawAngles () {
            var d = 50; //start line at (10, 20), move 50px away at angle of 30 degrees
            var angle = 80 * Math.PI/180;
            ctx.beginPath();
            ctx.moveTo(300,0);
            ctx.lineTo(300,600); //x, y
            ctx.moveTo(0,300);
            ctx.lineTo(600,300);
            ctx.moveTo(300,300);
            ctx.lineTo(600,100);
            ctx.arc(300,300,300,0,2*Math.PI);
            ctx.stroke();
        }

function getAngleX (x) {
            return x = x + (50 * Math.cos(Math.PI/6));
        }
        function getAngleY(y) {
            return  y = y + (50 * Math.sin(Math.PI/6));
        }

            //just animate this box to move at an angle from center down at 30 degrees
            $(".anotherBox").mouseenter(function(e) {
                pos =  $(this).position();
                box2X = pos.left;
                box2Y = pos.top;

                $(this).animate({
                    //top : $(window).outerHeight(),
                    top : getAngleY(box2Y)+"px",
                    left: getAngleX(box2X)+"px",
                }, "slow");
            });

function getSteps(angle) {

    var cos = Math.cos(angle),
        sin = Math.sin(angle);

    return {
        x: cos -sin,
        y: sin + cos
    }
}

function loop() {

    var x = i * step.x,  // scale using i
        y = i * step.y;

    ctx.fillRect(200 + x, 200 + y, 2, 2); // add to origin start point 200, 200

    i += 1;              // increase i

    if (i < length) requestAnimationFrame(loop);
}

function lineAtAngle(x1, y1, length, angle) {
    ctx.moveTo(x1, y1);
    ctx.lineTo(x1 + length * Math.cos(angle), y1 + length * Math.sin(angle));
}

var ctx = cv.getContext('2d');

var ball = {
    x:200, y:200,
    r : 30,
    vx : 0.4, vy:0.4
}

// when mouse moved that distance, ball speed norm will be 1
var speedNorm = 10;


function collide() {
    var dist = sq(ball.x - mx) + sq (ball.y-my);
    // too far from ball ?
    if (dist > sq(ball.r)) {
        collisionOnGoing = false;
        return;
    }
    // return if collision allready handled
    if (collisionOnGoing) return;
    var mouseDist =Math.sqrt( sq(mx-lastmx) + sq(my-lastmy) );
    // no collision if mouse too slow
    if (mouseDist<speedNorm/5) return;
    // launch the ball in current direction
    // with a speed relative to the mouse speed.
    var mouseAngle = Math.atan2(my-lastmy, mx-lastmx);
    ball.vx= (mouseDist / speedNorm ) * Math.cos(mouseAngle);
    ball.vy= (mouseDist / speedNorm ) * Math.sin(mouseAngle);
    collisionOnGoing = true;
}
var collisionOnGoing = false;

function animate() {
    requestAnimationFrame(animate);
    ctx.clearRect(0,0,400,400);
    // collide ball with mouse
    collide();
    // draw ball
    ctx.beginPath();
    ctx.arc(ball.x, ball.y, ball.r, 0, 6.3);
    ctx.fill();
    ctx.closePath();
    // move
    ball.x+=ball.vx;
    ball.y+=ball.vy;
    // collide with screen
    if (ball.x>400) ball.vx=-Math.abs(ball.vx);
    if (ball.x<0) ball.vx=Math.abs(ball.vx);
    if (ball.y>400) ball.vy=-Math.abs(ball.vy);
    if (ball.y<0) ball.vy=Math.abs(ball.vy);
}

animate();

//  ---  Mouse handling ---

addEventListener('mousemove', mouseMove);

var mx=-1, my=-1, lastmx=-1, lastmy=-1;
var cvRect = cv.getBoundingClientRect();
var cvLeft = cvRect.left;
var cvTop = cvRect.top;
function mouseMove(e) {
    lastmx = mx; lastmy=my;
    mx=e.clientX - cvLeft;
    my=e.clientY - cvTop;
}

function sq(x) { return x*x;  }