cY = 400;

​

let dX = cX / 1.5,

  dY = cY;

​

function setup() {

  createCanvas(2 * cX, 2 * cY);

}

​

function draw() {

  background(220, 220, 0);

  noFill();

  stroke('green');

  strokeWeight(2);

  ellipse(cX, cY, cX, cY); //_________________________ circle

  fill('lightblue');

  ellipse(cX, cY, dX, dY); //_________________________ ellipse

  strokeWeight(3);

  stroke('blue');

  for (let i = 0; i < 2 * PI; i += 0.05) { //_________ coded SAME ellipse for confirm

    let eX = dX / 2 * sin(i);

    let eY = -dY / 2 * cos(i);

    point(cX + eX, cY + eY);

  }

​

  for (let i = PI / 8; i < 2 * PI; i += PI / 4) { //__ sectors circle

    let eX = cX / 2 * sin(i);

    let eY = -cY / 2 * cos(i);

    noFill();

    strokeWeight(2);

    stroke('green');

    line(cX, cY, cX + eX, cY + eY);

    fill('red');

    noStroke();

    text(nf(i, 0, 2), cX + eX, cY + eY);

  }

​

  for (let i = 0.785398 / 2; i <= 6.6758843; i += 0.785398) { //___ sectors ellipse

    let eX = dX/2 * sin(i);

    let eY = -dY/2 * cos(i);

    stroke('blue');

    line(cX, cY, cX + eX, cY + eY);

  }

​

​

  //__________________________________________________ show mouse

  let m = createVector(mouseX - cX, mouseY - cY); //__ where is mouse as vector from center...

  mangle = m.heading();

​

  stroke('red');

  strokeWeight(1);

  line(cX, cY, cX + m.x, cY + m.y);

  strokeWeight(10);

  point(cX + m.x, cY + m.y);

  noStroke();

  text('x ' + mouseX + ' y ' + mouseY + ' m ' + nf(mangle, 0, 2), cX + m.x + 7, cY + m.y)

​

  //______________________________________________ there is a BUG in the angle ??

  let aoff = PI / 2;

  let eX = sin(mangle + aoff) / 2;

  let eY = -cos(mangle + aoff) / 2;

  let innerX = dX * eX;

  let innerY = dY * eY;

  let innerm = createVector(innerX, innerY); //____ ellipse point as vector from center...

  //print('innerm',innerm.heading());

  stroke('black');

  point(cX + innerX, cY + innerY);

​

  //_______________________________________________ make point / vector on the outer circle too

  let outerX = cX * eX;

  let outerY = cY * eY;

  let outerm = createVector(outerX, outerY); //____ point as vector from center...

  //print('outerm',outerm.heading());

  stroke('black');

  point(cX + outerX, cY + outerY);

​

}