def common_arg_parser():
    """
    Create an argparse.ArgumentParser for run_mujoco.py.
    """
    parser = arg_parser()
    parser.add_argument('--env', help='environment ID', type=str, default='Reacher-v2')
    parser.add_argument('--env_type', help='type of environment, used when the environment type cannot be automatically determined', type=str)
    parser.add_argument('--seed', help='RNG seed', type=int, default=None)
    parser.add_argument('--alg', help='Algorithm', type=str, default='ppo2')
    parser.add_argument('--num_timesteps', type=float, default=1e6),
    parser.add_argument('--network', help='network type (mlp, cnn, lstm, cnn_lstm, conv_only)', default=None)
    parser.add_argument('--gamestate', help='game state to load (so far only used in retro games)', default=None)
    parser.add_argument('--num_env', help='Number of environment copies being run in parallel. When not specified, set to number of cpus for Atari, and to 1 for Mujoco', default=None, type=int)
    parser.add_argument('--reward_scale', help='Reward scale factor. Default: 1.0', default=1.0, type=float)
    parser.add_argument('--save_path', help='Path to save trained model to', default=None, type=str)
    parser.add_argument('--save_video_interval', help='Save video every x steps (0 = disabled)', default=0, type=int)
    parser.add_argument('--save_video_length', help='Length of recorded video. Default: 200', default=200, type=int)
    parser.add_argument('--play', default=False, action='store_true')
    return parser