float theta;
color bg = #951F2B ;
color s = #F5F4D7 ;
color f = #A5A36C ;

void setup() {
  size(500, 500);
  strokeCap(SQUARE);
  frameRate(30);
}

void draw() {
  background(bg);
  fill(f);
  stroke(s);
  float gap = radians(15);
  float start = map(sin(theta), -1, 1, PI*1.5+gap, TAU+PI*0.5-gap);
  float end = map(sin(-theta), -1, 1, TAU+PI*0.5+gap, TAU+PI*1.5-gap);
  float sw = map(sin(theta), -1, 1, 80, 30);
  strokeWeight(sw);
  arc(width/2, height/2, 300, 300, start, end );

  theta += 0.0523;

  if (frameCount % 2 == 0 && frameCount < 121) saveFrame("image-####.gif");
}