OMG that pup is too cute, and that spotty nose is just too much!
In terms of mental stimulation, I find shaping games to be a great little mental exercise, whether that be a free-shaping game (like "the box game"), refining captured behaviors (ex: I work with my pup a lot on offering novel behaviors; usually if I go long enough just staring silently at her while in possession of food she'll start offering things and eventually offer a behavior I decide to make into a trick), and shaping a trick. Another great thing to do for mental exercise that is also very useful is to play recall games or impulse control games.
Also, if your dog is motivated by play or running I would recommend using that as a reinforcement in your training sessions as well as food. My dog looooves running and playing tug and especially to be chased, and so one of her most exciting reinforcements for when she does something really well or does a behavior perfectly that we've been working on for a long time is a game of tug followed by me chasing her around while she carries the toy- she gets so excited doing this sometimes she'll start making this weird bark/howl and play growling loudly, she sounds like a chainsaw.
Free shaping games:
- IMO/E playing shaping games is what creates an operant dog that offers behaviors, and this is really easy to achieve with a biddable dog like an Aussie
- a great one is the Box Game, where you present the dog with a box, wait for them to interact in some way with the box, and then reinforce that interaction and work towards refining it (for example, you start by reinforcing the dog for looking at the box, then build towards reinforcing the dog for sniffing the box, then for putting their mouth on it, then build towards them carry the box, either on cue or spontaneously- usually you aren't working towards putting anything on cue with this, the point is there's no pressure in this session because the dog is never actually doing anything wrong
- some people will come up with a command to indicate to the dog that they should start offering behaviors, like "what can you do?"
Refining captured behaviors and turning them into tricks:
- I don't have any more "named game" ideas, but other free-shaping activites might just including sitting around and waiting for the dog to do anything
(that might include getting bored and starting to sniff around, even), and then beginning to shape that into a more refined behavior and/or put it on cue as a trick
IME another great mental game is putting naturally reinforcing/ especially exciting behaviors/movements on cue. These will be different for every dog, and you'll have to observe yours and brain storm to figure out what they are for her; mine has some normal ones like sniffing and barking (which I'm utilizing by teaching a "speak" command as well as a "quiet" one) as well as some weird ones like jumping up on her back legs (she gets soo excited, and if she is just generally excited she'll often express it by rearing up), pawing with her feet (she always hits things when she gets excited and uses her feet a LOT in play, it's adorable), spinning (don't know why she likes it so much, but she starts play growling and barking excitedly when I have her do a bunch of quick spins for a toy). Once these exciting things are on cue, I then use them in play- they don't make the game less fun for the dog since they're such fun behaviors for them, but they do help to keep her from going into crazy puppy mode and sort of tone down the play if she starts getting overstimulated, because I've noticed my pup tends to have trouble calming down is she gets overstimulated. I think its partially her medium/high energy level and partially her age (10 months).
In terms of recall games:
- Restrained recalls (someone holds the dog while you run away from them, dance around, generally make them wiggly and excited, then just as you call them the person restraining them lets go; presumably they are trying to get to you the whole time and then it's super exciting when you finally let them. Note that this is not safe/fair to do if your dog reacts with aggression, fear, or anxiety when restrained in any way)
- Call the dog and start running the other way while vocalizing excitedly/acting fun/excited, proceed to have to dog chase you for a little bit and then reward (IME its usually more productive to use play/tug as a reward in this case rather than food)
- Throw food away from you (I usually start with a few feet and build up the distance I throw them as they start to get the way the game works), just after the dog has eaten the food you threw spread your feet a little bit, call the dog, and then throw the food just between/behind your feet so the dog goes through your legs, while saying "through"
- Do the same throw food away then call the dog routine as above but instead ask for the dog to sit at heel/sit in front/swing around from one side to the other and finish at heel, whatever
(search youtube for "recall games" and you'll get a lot of ideas)
For impulse control games, look up the "Its Yer Choice" game. Link below describing it:
It's Yer Choice: Teaching Self Control | Dog Trainer Games
Note: both recall games and Its Yer Choice were developed by Susan Garett, who is a great resource for fun training games useful for teaching recall, impulse control, building attention and attraction to the handler, and generally entertaining a young, energetic, smart dog. She has a great, interesting blog filled with great articles (although IMO it can be a little self-promotion-y, though not without cause).
Other great things to teach that are good, quick ways to exercise a dog mentally and physically are teaching sends to cones as well as jumps or barrel racing patterns. Once your dog has the idea of offering behaviors down its usually pretty easy to start teaching sends around cones, then working towards a barrel racing pattern. Below is a good example video of shaping a send around a cone:
Dog training for send-away | Clicker Training Videos | Video
Training a dog to go over a jump (which can be made of anything, like two jars holding up a broom handle or length of pipe- through preferably it would be made of something that can be easily knocked down to prevent injury) is also fairly easy, and you can find information on doing that through an internet search. I would suggest waiting until she's closer to 9 months or a year to do any jumping stuff, though.
Also, agility might be something good to look into- I've heard about a lot of success stories of shy, anxious dogs that gained confidence through agility. Also, with a smart, high energy dog like a young Aussie its a great way to channel that energy in a structured way, which I find can be more relaxing than just a whole lot of unstructured physical exercise might be.