itemClasses() {
  let result = [];
  let score = Math.floor(this.score * 2) / 2;
  let hasDecimal = score % 1 !== 0;
  let integer = Math.floor(score);
  for (let i = 0; i < integer; i++) {
    result.push(CLS_ON);
  }
  if (hasDecimal) {
    result.push(CLS_HALF);
  }
  while (result.length < LENGTH) {
    result.push(CLS_OFF);
  }
  return result;
}