My code for the final level at https://www.bloc.io/ruby-warrior. Could have been more efficient (pivot earlier when the closest object is a wall, don't bother healing when there are no enemies left) but I'm happy enough with it.

ruby-warrior.rb

class Player
  def play_turn(warrior)
  
    @health ||= warrior.health
    taking_damage = warrior.health < @health
    
    objects = warrior.look
    closest_enemy = objects.detect { |s| s.enemy? }
    closest_captive = objects.detect { |s| s.captive? }
    enemy_is_closer = closest_captive && closest_enemy && objects.index(closest_enemy) < objects.index(closest_captive)
    
    if !taking_damage && (!closest_captive || enemy_is_closer) && closest_enemy && objects.index(closest_enemy) < 3
      warrior.shoot!
    else
      space = warrior.feel
      
      if space.wall?
        warrior.pivot!
      elsif space.captive?
        warrior.rescue!
      elsif space.empty?
        if taking_damage
          if warrior.health < 10
            warrior.walk!(:backward)
          else
            warrior.walk!
          end
        elsif warrior.health < 20
          warrior.rest!
        else
          warrior.walk!
        end
      elsif space.enemy?
        warrior.attack!
      end
      @health = warrior.health
    end
  end
end