blameless

  // for a graph
  var balances = [];

  // constants
  var winnings =  1, 
      losses   = -1, 
      epsilon  = 0.05;

  function play(probOfWinning) {
      return Math.random() < probOfWinning ? winnings : losses;
  }

  for (var experiment = 0; experiment < 100; experiment++) {
      var balance = 0;
      for (var flip = 0; flip < 1000000; flip++) {
          if (flip % 3 == 0) { // game A
              balance += play(0.5 - epsilon);
          } else { // game B
              balance += Math.round(balance) % 3 == 0 ? play(1/10 - epsilon)
                                                      : play(3/4  - epsilon)
          }
      }
      balances.push(balance);
  }