I'm new to this forum, but have a strong Parelli background. I think there is a misunderstanding about the 7 games going on here. They are not the 7 games, they are 7 classes of games. Everything we do with a horse, even just standing next to them, falls into one of those classes. It took me a while to work this out, and it did not come from the level 1 or 2 pack but from learning from Parelli professionals.
To clarify:
Friendly game is being played anytime we are doing something too or around the horse where we expect no reaction from them. Swinging a rope lariat on there back while cantering towards a steer is Friendly game !
Porcupine Game is the game of steady pressure. This is pressure on any part of the horse that is not rhythmical. Thus applying pressure with the inside leg to ask the horse to bend around you is porcupine game. If they push back into that leg they are playing porcupine game on you. Often horses are playing and winning these games and we don't even know a game is being played

. Picking out hooves is a combination of Porcupine and Friendly game. Porcupine as you apply steady pressure to ask the hoof to be lifted, and friendly as you ask them to standstill and not move as you pick out the hoof. Dropping a hoof when finished just gave them a porcupine win by the way. I always place the toe of the hoof back on the ground and ask for relaxation before releasing. If you don't think the horse is playing porcupine with you in this situation then try placing the hoof next time you do the picking out and see what they do. If you can't control the placement of the hoof when it is in your hand, doing it with leg aids when riding is going to be a whole lot harder
Driving game is the game of rhythmical pressure. This is most often played on the ground with a stick and string, but can also be played when riding. For example when riding brideless if the horse does not respond to porcupine on the leg to turn then a stick and flag could add a little rhythmical pressure to the side of the nose to ask it to bend around. It should be able to be used to ask any part of the horse to move away from the rhythmic pressure applied whilst you are at a distance to the horse. Useful when circling on a 22 or 45 foot rope and then you ask for a step or two of sideways, or a hind quarter yield. It also allows the horse to be moved around without playing porcupine on the halter, too much of which threatens to make them dead to the halter. For example if the horses head goes down to eat when I am leading it rather than pulling hard on the halter I may use driving game on the hind quarters to move the hind feet and up pops the head.
YoYo game is not just about wriggling ropes to make your horse backup (which is driving game by the way). It is to do with getting energy to go forwards or backwards through your horse. Thus all transitions are YoYo game with an emphasis on straightness. Canter to trot to walk to halt to backup are all backwards YoYo, and the opposite is obviously forwards YoYo. The imagery is to help us to remember that like a YoYo downwards transitions should be balanced in terms of effort with upwards transitions.
Circling game is to help our horses learn their responsibilites of 1) Act like a partner, not a prey animal, 2) Maintain gait, 3)Maintain direction, 4) Look where you are going. To help in this the idea is to set your horse on a circle and then return to neutral (the feel of which you taught him in the Friendly game). The horse is then expected to maintain the gait and direction whilst you remain neutral in the middle applying no cues to keep going. If they break a responsibility then gently as possible, but as firmly as necessary, correct them, then back to neutral. This translates to the same responsibilities being upheld when riding. This means that once a direction around the rail of the school is set (for example), then with no further cues from the rider it should be maintained. The advantage to this concept is that when a cue arrives from the rider to change the activity is is much clearer to the horse that such a cue has been given. Nothing to pressure is better than a continual nagging to maintain gait to a different nagging to half pass.
Sideways game. This uses all the above games to get your horse to move away, or towards you sideways. It can be done using porcupine to simulate steady pressure of the leg for riding, or driving to allow for easy ground manoeuvres. Sideways towards is great for asking you horse to side pass into you as you sit on a fence ready to mount

. Once the basic game is learned it can then be used with the circling game online (or liberty) to ask your horse to track on 2, 3 or 4 tracks. This is a great exercise for making the horse more gymnastic leading to flying lead changes. Of course it will also help your horse with straightness. If they travel naturally off line then to them straight will feel like sideways. If we can get it to the point where we can ask for any degree of sideways we wish then we can ask for that little bit that brings them straight. Do this for long enough and it becomes their natural way of going.
Squeeze game. This is a game to modify their flight distance, and thus make them braver. It starts by asking them to pass between you and a wall (for example) then turn and face the "squeeze". This turn and face takes them quickly from a Right brain instinctual mind set to a Left brain thinking mindset. This mimics running from a lion instinctually for say 1/4 mile then turning and facing the threat to re-evaluate it. What we are doing is reducing that distance from 1/4 mile to a few paces. They then find benefit in trying to stay left brained (thinking) and put effort into it. Now lets think of other squeezes. Going through a gate/door. Entering a trailer which squeezes on all 4 sides. Mounting the horse which squeezes from above. Jumping the horse which squeezes by the jump pole from underneath and the rider on top (ever seen a horse that jumps 4 feet over a two foot jump, or goes in at trot and come out at canter. They are scared of this under the belly squeeze).
Sorry this is such a long post, but it is an important concept I am trying to get across. I hear too often that the 7 games have made a horse difficult or bored. This is almost certainly because they have only played the basic form and not progressed to use the 7 games as a tool kit to be utilised in many situations (in fact nearly all situations !).
They are also a very useful shorthand for discussing issues. My instructor only has to say to me "your horse is playing porcupine with you" and I can quickly understand what they mean and occasionally do the right thing to win the game
I'll finish here as to cover all aspects of this subject would actually mean writing out the entire Parelli program as the ideas here underpin much that is taught.