function setup() {

  createCanvas(windowWidth, windowHeight);

}

​

function draw(){

  background(0,255,0);

  dayCycle();

}

​

let xOff = 0;

let a,b;

let state = 2;

let sunHue1,sunHue2,sunHue3;

let skyHue1,skyHue2,skyHue3;

​

function dayCycle() {

  angleMode(radians)

  b = (windowHeight/4)*sin(xOff) + windowHeight/2;

  a = (-windowWidth/2 - 50)*cos(xOff) + windowWidth/2;

  if(state % 2 == 0){

    //sky

    if(xOff > -PI/2){

      skyHue1 = map(xOff, 0, -PI/2, 0, 35);

      skyHue2 = map(xOff, 0, -PI/2, 0, 57);

      skyHue3 = map(xOff, 0, -PI/2, 0, 93);

    }else{

      skyHue1 = map(xOff, -PI/2, -PI, 35, 0);

      skyHue2 = map(xOff, -PI/2, -PI, 57, 0);

      skyHue3 = map(xOff, -PI/2, -PI, 93, 0);

    }

    if(xOff > -PI/2){

      sunHue1 = map(xOff, 0, -PI/2, 232, 249);

      sunHue2 = map(xOff, 0, -PI/2, 119, 215);

      sunHue3 = map(xOff, 0, -PI/2, 66, 28);

    }else{

      sunHue1 = map(xOff, -PI/2, -PI, 249, 232);

      sunHue2 = map(xOff, -PI/2, -PI, 215, 119);

      sunHue3 = map(xOff, -PI/2, -PI, 28, 66);

    }

  }else{

    sunHue1 = 208;

    sunHue2 = 213;

    sunHue3 = 210;

    skyHue = 0;

  }

  noStroke();

  fill(skyHue1,skyHue2,skyHue3);

  rect(0, 0, windowWidth, windowHeight);

​

  fill(sunHue1,sunHue2,sunHue3);

  circle(a,b,100);  

  if(xOff <= -PI){

    xOff = 0;

    state++;

  }else{

    xOff-= 0.05;

  }

}