 op = ops[randInt(0, ops.length - 1)];
        let a=0, b=0, ans=0, text='';

        const pick = (ranges) => {
          const [min, max] = ranges;
          return randInt(min, max);
        };

        const ranges = {
          easy: {
            add: [[0,9],[0,9]],
            sub: [[0,9],[0,9]],
            mul: [[0,12],[0,12]],
            div: [[1,12],[0,12]], // divisor, quotient
          },
          medium: {
            add: [[10,99],[10,99]],
            sub: [[10,99],[10,99]],
            m