This should win every level (given enough tries):

  def play_turn(warrior)
    m = warrior.methods.grep(/.!$/).sample
    warrior.send(m, *([nil, :backward].sample if m != :rest!))
  end

(that sucker of :rest! that doesn't accept a direction argument!)

It's kind of amusing to see the warrior do random stuff like shooting arrows backwards and pivoting back in the worst possible moments. Too bad that Run button repeats the same movements if you didn't edit the source code somehow.

Great game and concept BTW!