text: import numpy as np
  from multiagent.core import World, Agent, Landmark
  from multiagent.scenario import BaseScenario
  
  class Scenario(BaseScenario):
      def make_world(self):
          world = World()
          # set any world properties first
          world.dim_c = 10
          world.collaborative = True  # whether agents share rewards
          # add agents
          world.agents = [Agent() for i in range(2)]
          for i, agent in enumerate(world.agents):
              agent.name = 'agent %d' % i
              agent.collide = False
          # add landmarks
          world.landmarks = [Landmark() for i in range(3)]
          for i, landmark in enumerate(world.landmarks):
              landmark.name = 'landmark %d' % i
              landmark.collide = False
              landmark.movable = False
          # make initial conditions
          self.reset_world(world)
          return world
  
      def reset_world(self, world):
          # assign goals to agents
          for agent in world.agents:
              agent.goal_a = None
              agent.goal_b = None
          # want other agent to go to the goal landmark
          world.agents[0].goal_a = world.agents[1]
          world.agents[0].goal_b = np.random.choice(world.landmarks)
          world.agents[1].goal_a = world.agents[0]
          world.agents[1].goal_b = np.random.choice(world.landmarks)
          # random properties for agents
          for i, agent in enumerate(world.agents):
              agent.color = np.array([0.25,0.25,0.25])               
          # random properties for landmarks
          world.landmarks[0].color = np.array([0.75,0.25,0.25]) 
          world.landmarks[1].color = np.array([0.25,0.75,0.25]) 
          world.landmarks[2].color = np.array([0.25,0.25,0.75]) 
          # special colors for goals
          world.agents[0].goal_a.color = world.agents[0].goal_b.color                
          world.agents[1].goal_a.color = world.agents[1].goal_b.color                               
          # set random initial states
          for agent in world.agents:
              agent.state.p_pos = np.random.uniform(-1,+1, world.dim_p)
              agent.state.p_vel = np.zeros(world.dim_p)
              agent.state.c = np.zeros(world.dim_c)
          for i, landmark in enumerate(world.landmarks):
              landmark.state.p_pos = np.random.uniform(-1,+1, world.dim_p)
              landmark.state.p_vel = np.zeros(world.dim_p)
  
      def reward(self, agent, world):
          if agent.goal_a is None or agent.goal_b is None:
              return 0.0
          dist2 = np.sum(np.square(agent.goal_a.state.p_pos - agent.goal_b.state.p_pos))
          return -dist2
  
      def observation(self, agent, world):
          # goal color
          goal_color = [np.zeros(world.dim_color), np.zeros(world.dim_color)]
          if agent.goal_b is not None:
              goal_color[1] = agent.goal_b.color 
  
          # get positions of all entities in this agent's reference frame
          entity_pos = []
          for entity in world.landmarks:
              entity_pos.append(entity.state.p_pos - agent.state.p_pos)
          # entity colors
          entity_color = []
          for entity in world.landmarks:
              entity_color.append(entity.color)
          # communication of all other agents
          comm = []
          for other in world.agents:
              if other is agent: continue
              comm.append(other.state.c)
          return np.concatenate([agent.state.p_vel] + entity_pos + [goal_color[1]] + comm)
              