Draw O's in Tic Tac Toe Board

draw-ttt-o.js

drawO(x, y){
  let halfCellSize = (0.5 * this.cellSize);
  let centerX  = x + halfCellSize;
  let centerY  = y + halfCellSize;
  let radius   = (this.cellSize * 0.7) / 2;
  let endAngle = 2 * Math.PI;

  this.ctx.lineWidth   = this.oLineWidth;
  this.ctx.strokeStyle = this.oStyle;
  this.ctx.beginPath();
  this.ctx.arc(centerX, centerY, radius, 0, endAngle);
  this.ctx.stroke();
}