Rewritten some methods

warrior.rb

class Player
  @stairs = false
  @wall = false
  @warrior
 
  def play_turn(warrior)
    @warrior = warrior
    if damaged_from_behind
      warrior.shoot!(:backward)
    else
      should_look
    end
    @health = warrior.health
  end
  
  def can_fight
    @warrior.health > 15
  end
  
  def taking_damage?
    @warrior.health < @health
  end
  
  def injured
    if taking_damage?
      return @warrior.walk!(can_fight? ? :forward : :backward)
    else
      @warrior.rest!
    end
  end
  
  def explore
    if @warrior.feel.stairs?
      @stairs = true
      return @wall ? @warrior.walk! : @warrior.pivot!
    end
    if @warrior.feel.wall?
      @wall = true
      return @warrior.pivot!
    end
    
    @warrior.walk!
  end
  
  def first_non_empty(spaces)
    spaces.each do |space|
      return "enemy" if space.enemy?
      return "captive" if space.captive?
    end
    "blank"
  end  
  
  def damaged_from_behind
    @warrior.health < 20 && taking_damage? && first_non_empty(@warrior.look(:backward)) == "enemy"
  end
  
  def check_health
    @warrior.health < 20 ? injured : explore
  end
  
  def should_move
    return @warrior.attack! if @warrior.feel.enemy?
    return @warrior.rescue! if @warrior.feel.captive?

    check_health
  end
  
  def should_look
    if first_non_empty(@warrior.look) == "enemy"
      @warrior.shoot!
    else
      should_move
    end
  end
  
end

The nested if statements in injured and explore still bug me a bit. Not a huge deal but I might approach explore like:

def explore
  @stairs = @warrior.feel.stairs?
  @wall = @warrior.feel.wall?

  @wall ? @warrior.pivot : @warrior.walk
end

That said, I simplified the logic you had there a bit. I'm not sure why if you feel stairs you then check to see if there is a wall and walk if there is a wall but pivot if there is not. That doesn't make much sense to me. I might be missing something though.

Injured I might write something like:

def injured
  if @warrior.taking_damage
    return @warrior.walk!(can_fight? ? :forward : :backward)
  else
    @warrior.rest!
  end
end

That's pretty much it. Sorry to just show you how I'd do it but sometimes its hard to make suggestions until I sit down and write through the code. Most of them are just syntactic sugar that ruby makes easy. Let me know if you have any questions.

Nice, that looks better.